feat: KB quality improvements — CHECK constraints, FTS coverage, outcome validation (#90)

[four-bytes-robby]

Summary

Ports quality improvements from the standalone four-opencode-knowledge plugin to brain's src/knowledge/.

Changes

Schema — src/schema.ts

• CHECK constraints on confidence (0.0–1.0), review_state (valid enum), outcome (valid enum)
• Migration triggers for existing databases (follows migrateEntityTypeCheck pattern with retry)
• FTS rebuild to include entry_key, kind, entity_type (previously only 5 columns)

Runtime — src/knowledge/store.ts

• Outcome validation in kbRecord() — rejects invalid outcomes before INSERT with clear error message

Verification

• ✅ Build passes
• ✅ All 247 tests pass
• ✅ Confidence migration applies on first run (visible in test logs)
• ✅ FTS rebuild non-destructive (content table untouched)

Closes #90

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Summary by cubic

Improves knowledge base data quality by enforcing constraints, making outcome validation unconditional, and rebuilding FTS for better search. Implements the KB quality work from #90.

• New Features

  • CHECK constraints: confidence (0.0–1.0), review_state enum, occurrence outcome enum.
  • Outcome validation in kbRecord() now always runs before insert and throws a clear error with allowed values.

• Migration

  • Rebuilds FTS to include entry_key, kind, entity_type and recreates sync triggers with full 8-column coverage; content table remains unchanged.
  • Adds retrying trigger-based migrations for existing DBs to enforce the new checks on insert/update.

^{Written for commit 0afa508. Summary will update on new commits.}

[cubic-dev-ai]

2 issues found across 3 files

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