Implement hash ID generation in CreateIssue

Replace sequential ID generation with hash-based IDs in CreateIssue function.

## Current Behavior (internal/storage/sqlite/sqlite.go)
```go
func (s *SQLiteStorage) CreateIssue(ctx context.Context, issue *types.Issue) error {
    // ID comes from auto-increment counter
    // Collisions possible across clones
}
```

## New Behavior
```go
func (s *SQLiteStorage) CreateIssue(ctx context.Context, issue *types.Issue) error {
    // Generate hash ID if not provided
    if issue.ID == "" {
        issue.ID = idgen.GenerateHashID(
            issue.Title,
            issue.Description,
            time.Now(),
            s.workspaceID,
        )
    }

    // Assign next alias
    issue.Alias = s.getNextAlias()

    // Insert with hash ID + alias
    // ...
}
```

## Workspace ID Generation
Add to database initialization:
```go
// Generate stable workspace ID (persisted in .beads/workspace_id)
workspaceID := getOrCreateWorkspaceID()
```

Options for workspace ID:
1. Hostname + random suffix
2. UUID (random)
3. Git remote URL hash (deterministic per repo)

Recommended: Option 3 (git remote hash) for reproducibility

## Hash Collision Detection
```go
// On insert, check for collision (unlikely but possible)
existing, err := s.GetIssue(ctx, issue.ID)
if err == nil {
    // Hash collision! Add random suffix and retry
    issue.ID = issue.ID + "-" + randomSuffix(4)
}
```

## Files to Create/Modify
- internal/types/id_generator.go (new)
- internal/storage/sqlite/sqlite.go (CreateIssue)
- internal/storage/sqlite/workspace.go (new - workspace ID management)
- .beads/workspace_id (new file, git-ignored)

## Testing
- Test hash ID generation is deterministic
- Test collision detection and retry
- Test workspace ID persistence
- Benchmark: hash generation performance (<1μs)


Investigation & Proof of Concept

Validate that MCP Agent Mail works as expected and delivers promised benefits before committing to full integration.

POC completed successfully:
✅ bd-muls: Server installed and tested
✅ bd-27xm: MCP tool execution issues resolved
✅ [deleted:bd-6hji]: File reservation collision prevention validated
✅ bd-htfk: Latency benchmarking shows 20-50x improvement
✅ bd-pmuu: ADR 002 created documenting integration decision

Results validate Agent Mail benefits:
- Collision prevention works (exclusive file reservations)
- Latency: <100ms (vs 2000-5000ms git sync)
- Lightweight deployment (<50MB memory)
- Optional/non-intrusive integration approach validated

Next: bd-wfmw (Integration Layer Implementation)


bd validate - Comprehensive health check

Run all validation checks in one command.

Checks:
- Duplicates
- Orphaned dependencies
- Test pollution
- Git conflicts

Supports --fix-all for auto-repair.

Depends on bd-cbed9619.1, bd-0dcea000, bd-31aab707, bd-9826b69a.

Files: cmd/bd/validate.go (new)


Fix daemon exiting after 5s on macOS due to PID 1 parent monitoring

GitHub issue #278 reports that the daemon exits after <=5 seconds on macOS because it incorrectly treats PID 1 (launchd) as a dead parent.

When the daemon detaches on macOS, it gets reparented to PID 1 (launchd), which is the init process. The checkParentProcessAlive function was incorrectly treating PID 1 as a sign that the parent died.

Fixed by changing the logic to treat PID 1 as a valid parent for detached daemons.