Add collision detection infrastructure to identify conflicts during
JSONL import when branches diverge and create issues with the same ID.
New files:
- internal/storage/sqlite/collision.go: Core collision detection logic
- detectCollisions() categorizes issues as exact matches, collisions, or new
- compareIssues() identifies which fields differ between issues
- CollisionDetail provides detailed collision reporting
- internal/storage/sqlite/collision_test.go: Comprehensive test suite
- Tests exact matches, new issues, and various collision scenarios
- Tests multi-field conflicts and edge cases
- All tests passing
This lays the foundation for bd-13 through bd-17 (reference scoring,
ID remapping, CLI flags, and documentation).
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
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