WIP: Implement content-hash based collision resolution (bd-89)

- Replace timestamp-based collision scoring with deterministic content hashing
- Add hashIssueContent() using SHA-256 of all substantive fields
- Modify ScoreCollisions to compare hashes and set RemapIncoming flag
- Update RemapCollisions to handle both directions (remap incoming OR existing)
- Add CollisionDetail.RemapIncoming field to control which version gets remapped
- Add unit tests for hash function and deterministic collision resolution

Status: Hash-based resolution works correctly, but TestTwoCloneCollision still
fails due to missing rename detection. After Clone B resolves collision,
Clone A needs to recognize its issue was remapped to a different ID.

Next: Add content-based rename detection during import to prevent
re-resolving already-resolved collisions.

Progress on bd-86.

Amp-Thread-ID: https://ampcode.com/threads/T-b19b49e8-b52a-463d-b052-8a526a500260
Co-authored-by: Amp <amp@ampcode.com>

.beads/beads.jsonl

@@ -83,4 +83,7 @@
 {"id":"bd-84","title":"Remove unreachable utility functions","description":"Several small utility functions are unreachable:\n\nFiles to clean:\n1. `internal/storage/sqlite/hash.go` - `computeIssueContentHash` (line 17)\n   - Check if entire file can be deleted if only contains this function\n\n2. `internal/config/config.go` - `FileUsed` (line 151)\n   - Delete unused config helper\n\n3. `cmd/bd/git_sync_test.go` - `verifyIssueOpen` (line 300)\n   - Delete dead test helper\n\n4. `internal/compact/haiku.go` - `HaikuClient.SummarizeTier2` (line 81)\n   - Tier 2 summarization not implemented\n   - Options: implement feature OR delete method\n\nImpact: Removes 50-100 LOC depending on decisions","acceptance_criteria":"- Remove unreachable functions\n- If entire files can be deleted (like hash.go), delete them\n- For SummarizeTier2: decide to implement or delete, document decision\n- All tests pass: `go test ./...`\n- Verify no callers exist for each function","status":"open","priority":2,"issue_type":"task","created_at":"2025-10-28T16:20:02.434573-07:00","updated_at":"2025-10-28T16:20:02.434573-07:00"}
 {"id":"bd-85","title":"Event-driven daemon architecture","description":"Replace 5-second polling sync loop with event-driven architecture that reacts instantly to changes. Eliminates stale data issues while reducing CPU ~60%. Key components: FileWatcher (fsnotify), Debouncer (500ms), RPC mutation events, optional git hooks. Target latency: \u003c500ms (vs 5000ms). See event_driven_daemon.md for full design.","status":"open","priority":1,"issue_type":"epic","created_at":"2025-10-28T16:30:27.39845-07:00","updated_at":"2025-10-28T16:30:27.39845-07:00"}
 {"id":"bd-86","title":"Make two-clone workflow actually work (no hacks)","description":"TestTwoCloneCollision proves beads CANNOT handle two independent clones filing issues simultaneously. This is the basic collaborative workflow and it must work cleanly.\n\nTest location: beads_twoclone_test.go\n\nThe test creates two git clones, both file issues with same ID (test-1), --resolve-collisions remaps clone B's to test-2, but after sync:\n- Clone A has test-1=\"Issue from clone A\", test-2=\"Issue from clone B\"  \n- Clone B has test-1=\"Issue from clone B\", test-2=\"Issue from clone A\"\n\nThe TITLES are swapped! Both clones have 2 issues but with opposite title assignments.\n\nWe've tried many fixes (per-project daemons, auto-sync, lamport hashing, precommit hooks) but nothing has made the test pass.\n\nGoal: Make the test pass WITHOUT hacks. The two clones should converge to identical state after sync.","acceptance_criteria":"1. TestTwoCloneCollision passes without EXPECTED FAILURE\n2. Both clones converge to identical issue database\n3. No manual conflict resolution required\n4. Git status clean in both clones\n5. bd ready output identical in both clones","status":"open","priority":0,"issue_type":"epic","created_at":"2025-10-28T16:34:53.278793-07:00","updated_at":"2025-10-28T16:34:53.278793-07:00"}
+{"id":"bd-87","title":"Implement content-hash based collision resolution for deterministic convergence","description":"The current collision resolution uses creation timestamps to decide which issue to keep vs. remap. This is non-deterministic when two clones create issues at nearly the same time.\n\nRoot cause of bd-86:\n- Clone A creates test-1=\"Issue from clone A\" at T0\n- Clone B creates test-1=\"Issue from clone B\" at T0+30ms\n- Clone B syncs first, remaps Clone A's to test-2\n- Clone A syncs second, sees collision, remaps Clone B's to test-2\n- Result: titles are swapped between clones\n\nSolution:\n- Use content-based hashing (title + description + priority + type)\n- Deterministic winner: always keep issue with lower hash\n- Same collision on different clones produces same result (idempotent)\n\nImplementation:\n- Modify ScoreCollisions in internal/storage/sqlite/collision.go\n- Replace timestamp-based scoring with content hash comparison\n- Ensure hash function is stable across platforms","status":"open","priority":0,"issue_type":"task","created_at":"2025-10-28T17:04:06.145646-07:00","updated_at":"2025-10-28T17:04:06.145646-07:00"}
+{"id":"bd-88","title":"Add test case for symmetric collision (both clones create same ID simultaneously)","description":"TestTwoCloneCollision demonstrates the problem, but we need a simpler unit test for the collision resolver itself.\n\nTest should verify:\n- Two issues with same ID, different content\n- Content hash determines winner deterministically  \n- Result is same regardless of which clone imports first\n- No title swapping occurs\n\nThis can be a simpler test than the full integration test.","status":"open","priority":1,"issue_type":"task","created_at":"2025-10-28T17:04:06.146021-07:00","updated_at":"2025-10-28T17:04:06.146021-07:00","dependencies":[{"issue_id":"bd-88","depends_on_id":"bd-86","type":"blocks","created_at":"2025-10-28T17:04:06.147846-07:00","created_by":"daemon"}]}
+{"id":"bd-89","title":"Implement content-hash based collision resolution for deterministic convergence","description":"The current collision resolution uses creation timestamps to decide which issue to keep vs. remap. This is non-deterministic when two clones create issues at nearly the same time.\n\nRoot cause of bd-86:\n- Clone A creates test-1=\"Issue from clone A\" at T0\n- Clone B creates test-1=\"Issue from clone B\" at T0+30ms\n- Clone B syncs first, remaps Clone A's to test-2\n- Clone A syncs second, sees collision, remaps Clone B's to test-2\n- Result: titles are swapped between clones\n\nSolution:\n- Use content-based hashing (title + description + priority + type)\n- Deterministic winner: always keep issue with lower hash\n- Same collision on different clones produces same result (idempotent)\n\nImplementation:\n- Modify ScoreCollisions in internal/storage/sqlite/collision.go\n- Replace timestamp-based scoring with content hash comparison\n- Ensure hash function is stable across platforms","notes":"Current status: Hash-based collision resolution is implemented and unit-tested, but TestTwoCloneCollision still fails.\n\nRoot cause: After Clone B resolves collision (test-1=B, test-2=A), Clone A syncs and sees:\n- DB: test-1=A\n- JSONL: test-1=B, test-2=A\n\nClone A detects collision on test-1 and tries to resolve it independently. But it should recognize that test-2 in JSONL is actually ITS OWN issue (content match).\n\nSolution: Add content-based rename detection during import. If incoming has different ID but same content as existing issue, treat as rename/remap rather than collision.\n\nFiles modified so far:\n- internal/storage/sqlite/collision.go (hashIssueContent, ScoreCollisions, RemapCollisions)\n- internal/storage/sqlite/collision_hash_test.go (new unit tests)\n\nNext steps:\n1. Add rename detection logic to DetectCollisions\n2. When importing, match issues by content hash across IDs\n3. Delete old ID, accept new ID for content matches\n4. Only apply collision resolution for true conflicts","status":"in_progress","priority":0,"issue_type":"task","created_at":"2025-10-28T17:04:11.530026-07:00","updated_at":"2025-10-28T17:10:28.522668-07:00","dependencies":[{"issue_id":"bd-89","depends_on_id":"bd-86","type":"blocks","created_at":"2025-10-28T17:04:18.149604-07:00","created_by":"daemon"}]}
 {"id":"bd-9","title":"Document bd edit command and verify MCP exclusion","description":"Follow-up from PR #152:\n1. Add \"bd edit\" to AGENTS.md with \"Humans only\" note\n2. Verify MCP server doesn't expose bd edit command\n3. Consider adding test for command registration","status":"open","priority":2,"issue_type":"task","created_at":"2025-10-26T13:23:47.982295-07:00","updated_at":"2025-10-27T22:22:23.815469-07:00"}