bd migrate --update-repo-id triggers auto-import that resurrects deleted issues

**Bug:** Running `bd migrate --update-repo-id` can resurrect previously deleted issues from git history.

## What Happened

User deleted 490 closed issues:
- Deletion committed successfully (06d655a) with JSONL at 48 lines
- Database had 48 issues after deletion
- User ran `bd migrate --update-repo-id` to fix legacy database
- Migration triggered daemon auto-import
- JSONL had been restored to 538 issues (from commit 6cd3a32 - before deletion)
- Auto-import loaded the old JSONL over the cleaned database
- Result: 490 deleted issues resurrected

## Root Cause

The auto-import logic in `cmd/bd/sync.go:130-136`:
```go
if isJSONLNewer(jsonlPath) {
    fmt.Println("→ JSONL is newer than database, importing first...")
    if err := importFromJSONL(ctx, jsonlPath, renameOnImport); err != nil {
```

This checks if JSONL mtime is newer than database and auto-imports. The problem:
1. Git operations (pull, merge, checkout) can restore old JSONL files
2. Restored file has recent mtime (time of git operation)
3. Auto-import sees "newer" JSONL and imports it
4. Old data overwrites current database state

## Timeline

- 19:59: Commit 6cd3a32 restored JSONL to 538 issues from d99222d
- 20:22: Commit 3520321 (bd sync)
- 20:23: Commit 06d655a deleted 490 issues → JSONL now 48 lines
- 20:23: User ran `bd migrate --update-repo-id`
- Migration completed, daemon started
- Daemon saw JSONL (restored earlier to 538) was "newer" than database
- Auto-import resurrected 490 deleted issues

## Impact

- **Critical data loss bug** - user deletions can be undone silently
- Affects any workflow that uses git branches, merges, or checkouts
- Auto-import has no safety checks against importing older data
- Users have no warning that old data will overwrite current state

## Fix Options

1. **Content-based staleness** (not mtime-based)
   - Compare JSONL content hash vs database content hash
   - Only import if content actually changed
   - Prevents re-importing old data with new mtime

2. **Database timestamp check**
   - Store "last export timestamp" in database metadata
   - Only import JSONL if it's newer than last export
   - Prevents importing old JSONL after git operations

3. **User confirmation**
   - Before auto-import, show diff of what will change
   - Require confirmation for large changes (>10% issues affected)
   - Safety valve for destructive imports

4. **Explicit sync mode**
   - Disable auto-import entirely
   - Require explicit `bd sync` or `bd import` commands
   - Trade convenience for safety

## Recommended Solution

Combination of #1 and #2:
- Add `last_export_timestamp` to database metadata
- Check JSONL mtime > last_export_timestamp before importing
- Add content hash check as additional safety
- Show warning if importing would delete >10 issues

This preserves auto-import convenience while preventing data loss.

## Files Involved

- `cmd/bd/sync.go:130-136` - Auto-import logic
- `cmd/bd/daemon_sync.go` - Daemon export/import cycle
- `internal/autoimport/autoimport.go` - Staleness detection

## Reproduction Steps

1. Create and delete some issues, commit to git
2. Checkout an earlier commit (before deletion)
3. Checkout back to current commit
4. JSONL file now has recent mtime but old content
5. Run any bd command that triggers auto-import
6. Deleted issues are resurrected


Remove unreachable utility functions

Several small utility functions are unreachable:

Files to clean:
1. `internal/storage/sqlite/hash.go` - `computeIssueContentHash` (line 17)
   - Check if entire file can be deleted if only contains this function

2. `internal/config/config.go` - `FileUsed` (line 151)
   - Delete unused config helper

3. `cmd/bd/git_sync_test.go` - `verifyIssueOpen` (line 300)
   - Delete dead test helper

4. `internal/compact/haiku.go` - `HaikuClient.SummarizeTier2` (line 81)
   - Tier 2 summarization not implemented
   - Options: implement feature OR delete method

Impact: Removes 50-100 LOC depending on decisions


Add tombstone doctor checks

Add bd doctor checks for: unmigrated deletions.jsonl, stale deletions.jsonl in Phase 3, tombstones expiring soon. Per design bd-dli.


Test numeric 1


Issue 1


Extract daemon sync functions to daemon_sync.go


Add comprehensive tests for show.go commands (show, update, edit, close)

Need to add tests for cmd/bd/show.go which contains show, update, edit, and close commands.

**Challenge**: The existing test patterns use rootCmd.SetArgs() and rootCmd.Execute(), but the global `store` variable needs to match what the commands use. Initial attempt created tests that failed with "no issue found" because the test's store instance wasn't the same as the command's store.

**Files to test**:
- show.go (contains showCmd, updateCmd, editCmd, closeCmd)

**Coverage needed**:
- show command (single issue, multiple issues, JSON output, with dependencies, with labels, with compaction)
- update command (status, priority, title, assignee, description, multiple fields, multiple issues)
- edit command (requires $EDITOR, may need mocking)
- close command (single issue, multiple issues, with reason, JSON output)

**Test approach**:
1. Study working test patterns in init_test.go, list_test.go, etc.
2. Ensure BEADS_NO_DAEMON=1 is set
3. Properly initialize database with bd init
4. Use the command's global store, not a separate instance
5. May need to reset global state between tests

**Success criteria**:
- All test functions pass
- Coverage for show.go increases significantly
- Tests follow existing patterns in cmd/bd/*_test.go


Parent: bd-imj

Ensure deletions.jsonl is tracked in git (not ignored).

Update bd init and gitignore upgrade logic to:
1. NOT add deletions.jsonl to .gitignore
2. Ensure it is committed alongside beads.jsonl

The file must be in git for cross-clone propagation to work.

Acceptance criteria:
- bd init does not ignore deletions.jsonl
- Existing .gitignore files are not broken
- File appears in git status when modified


Update AGENTS.md with event-driven mode

Document BEADS_DAEMON_MODE env var. Explain opt-in during Phase 1. Add troubleshooting for watcher failures.


Add TestThreeCloneCollision for regression protection

Add a 3-clone collision test to document behavior and provide regression protection.

Purpose:
- Verify content convergence regardless of sync order
- Document the ID non-determinism behavior (IDs may be assigned differently based on sync order)
- Provide regression protection for multi-way collisions

Test design:
- 3 clones create same ID with different content
- Test two different sync orders (A→B→C vs C→A→B)
- Assert content sets match (ignore specific ID assignments)
- Add comment explaining ID non-determinism is expected behavior

Known limitation:
- Content always converges correctly (all issues present with correct titles)
- Numeric ID assignments (test-2 vs test-3) depend on sync order
- This is acceptable if content convergence is the primary goal


Benchmark git traffic reduction

Automated benchmark comparing git operations with/without Agent Mail.

Acceptance Criteria:
- Script that processes 50 issues
- Counts git operations (pull, commit, push)
- Generates comparison report
- Verifies ≥70% reduction
- Fails if regression detected

File: tests/benchmarks/git_traffic.py

Output: Without Agent Mail: 450 git operations, With Agent Mail: 135 git operations, Reduction: 70%

Implemented automated benchmark script with following features:
- Processes configurable number of issues (default 50)
- Compares git operations in two modes: git-only vs Agent Mail
- Generates detailed comparison report with statistics
- Exit code reflects pass/fail based on 70% reduction target
- Results: 98.5% reduction (200 ops → 3 ops) for 50 issues

Files created:
- tests/benchmarks/git_traffic.py (main benchmark script)
- tests/benchmarks/README.md (documentation)
- tests/benchmarks/git_traffic_50_issues.md (sample results)

The benchmark vastly exceeds the 70% target, showing 98.5% reduction.


Support --reason flag in daemon mode for reopen command

The reopen.go command has a TODO at line 61 to add reason as a comment once RPC supports AddComment. Currently --reason flag is ignored in daemon mode with a warning.


Auto-detect issue prefix from existing JSONL in 'bd init'

When running `bd init` in a fresh clone with existing JSONL, it should auto-detect the issue prefix from the JSONL file instead of requiring `--prefix`.

Currently you must specify `--prefix ef` manually. But the JSONL file already contains issues like `ef-1it`, `ef-1jp` etc., so the prefix is known.

**Ideal UX**:
```
$ bd init
Detected issue prefix 'ef' from existing JSONL (38 issues).
✓ Database initialized...
```

This would make fresh clone hydration a single command: `bd init` with no flags.


Remove obsolete stale.go command (executor tables never implemented)


Update MCP server for hash IDs

Update beads-mcp server to support hash IDs and aliases.

## Changes Needed

### 1. MCP Function Signatures (No Change)
Functions already use issue IDs as strings, so they work with hash IDs:

```python
# These already work!
beads_show(issue_id: str)           # Accepts bd-af78e9a2 or #42
beads_update(issue_id: str, ...)    # Accepts both formats
beads_close(issue_ids: List[str])   # Accepts both formats
```

### 2. Add Alias Resolution Helper
File: integrations/beads-mcp/src/beads_mcp/server.py

```python
def resolve_issue_id(issue_id: str) -> str:
    """Resolve alias to hash ID if needed."""
    # Hash ID: pass through
    if issue_id.startswith('bd-') and len(issue_id) == 11:
        return issue_id

    # Alias: #42 or 42
    alias_str = issue_id.lstrip('#')
    try:
        alias = int(alias_str)
        # Call bd to resolve
        result = subprocess.run(
            ['bd', 'alias', 'find', f'bd-{alias}'],
            capture_output=True, text=True
        )
        if result.returncode == 0:
            return result.stdout.strip()
    except ValueError:
        pass

    # Invalid format
    raise ValueError(f"Invalid issue ID: {issue_id}")
```

### 3. Update Response Formatting
Show aliases in responses:

```python
@server.call_tool()
async def beads_show(issue_id: str) -> List[TextContent]:
    resolved_id = resolve_issue_id(issue_id)

    result = subprocess.run(['bd', 'show', resolved_id], ...)

    # Parse response and add alias info
    # Format: "bd-af78e9a2 (alias: #42)"
    ...
```

### 4. Add beads_alias_* Functions

```python
@server.call_tool()
async def beads_alias_list() -> List[TextContent]:
    """List all alias mappings."""
    result = subprocess.run(['bd', 'alias', 'list'], ...)
    return [TextContent(type="text", text=result.stdout)]

@server.call_tool()
async def beads_alias_set(alias: int, issue_id: str) -> List[TextContent]:
    """Manually assign alias to issue."""
    result = subprocess.run(['bd', 'alias', 'set', str(alias), issue_id], ...)
    return [TextContent(type="text", text=result.stdout)]

@server.call_tool()
async def beads_alias_compact() -> List[TextContent]:
    """Compact aliases to fill gaps."""
    result = subprocess.run(['bd', 'alias', 'compact'], ...)
    return [TextContent(type="text", text=result.stdout)]
```

### 5. Update Documentation
File: integrations/beads-mcp/README.md

```markdown
## Issue IDs (v2.0+)

The MCP server accepts both hash IDs and aliases:

```python
# Using hash IDs
await beads_show(issue_id="bd-af78e9a2")

# Using aliases
await beads_show(issue_id="#42")
await beads_show(issue_id="42")  # Shorthand
```

## Alias Management

New functions for alias control:

- `beads_alias_list()` - List all alias mappings
- `beads_alias_set(alias, issue_id)` - Manually assign alias
- `beads_alias_compact()` - Compact aliases to fill gaps

## Migration

After migrating to hash IDs:
1. Update beads-mcp: `pip install --upgrade beads-mcp`
2. Restart MCP server
3. All existing workflows continue to work
```

### 6. Version Compatibility
Detect and handle both v1.x and v2.0 formats:

```python
def detect_beads_version() -> str:
    """Detect if beads is using sequential or hash IDs."""
    result = subprocess.run(['bd', 'list', '-n', '1'], ...)
    first_id = parse_first_issue_id(result.stdout)

    if first_id.startswith('bd-') and len(first_id) > 11:
        return '2.0'  # Hash ID
    else:
        return '1.x'  # Sequential ID

# On startup
beads_version = detect_beads_version()
logger.info(f"Detected beads version: {beads_version}")
```

## Testing

### Unit Tests
File: integrations/beads-mcp/tests/test_hash_ids.py

```python
def test_resolve_hash_id():
    """Hash IDs pass through unchanged."""
    assert resolve_issue_id("bd-af78e9a2") == "bd-af78e9a2"

def test_resolve_alias():
    """Aliases resolve to hash IDs."""
    # Mock bd alias find command
    assert resolve_issue_id("#42") == "bd-af78e9a2"
    assert resolve_issue_id("42") == "bd-af78e9a2"

def test_invalid_id():
    """Invalid IDs raise ValueError."""
    with pytest.raises(ValueError):
        resolve_issue_id("invalid")
```

### Integration Tests
```python
async def test_show_with_hash_id(mcp_server):
    result = await mcp_server.beads_show(issue_id="bd-af78e9a2")
    assert "bd-af78e9a2" in result[0].text

async def test_show_with_alias(mcp_server):
    result = await mcp_server.beads_show(issue_id="#42")
    assert "bd-af78e9a2" in result[0].text  # Resolved
```

## Backward Compatibility
The MCP server should work with both:
- Beads v1.x (sequential IDs)
- Beads v2.0+ (hash IDs)

Detection happens at runtime based on issue ID format.

## Files to Modify
- integrations/beads-mcp/src/beads_mcp/server.py
- integrations/beads-mcp/README.md
- integrations/beads-mcp/tests/test_hash_ids.py (new)
- integrations/beads-mcp/pyproject.toml (bump version)

## Deployment
```bash
cd integrations/beads-mcp
# Bump version to 2.0.0
poetry version 2.0.0
# Publish to PyPI
poetry publish --build
```