fix(coding-agents): surface missing sqlite3 instead of silently disabling Devin retain

[r266-tech]

Summary

• distinguish a successful empty Devin transcript query from sqlite execution, schema, and parse failures
• keep Stop hooks fail-open while logging and recording retain_transcript_failed diagnostics
• probe sqlite3's required JSON query mode during Devin installation and warn without blocking hook setup

The sqlite CLI bridge remains dependency-free for Node; users now get an actionable signal when its external prerequisite cannot read transcripts. Thanks @ichoosetoaccept for isolating the failure mode in #3125.

Testing

• npm test (267 tests)
• npx tsc --noEmit
• npm run build
• Prettier check on all changed files

CI note

Current main contains #3109's canonical OpenAPI update but not its generated skills/hindsight-docs/references/openapi.json mirror. The required generated-file check reproduced that base drift on this PR, so a separate commit synchronizes the mirror byte-for-byte with hindsight-docs/static/openapi.json; no API source or schema is changed here.

Fixes #3125

[nicoloboschi]

see #3175