fix(session-ingest): treat creation default title as placeholder for agent-generated titles

[eshurakov]

Problem

#4852 stopped agent-generated titles from clobbering user renames by only promoting the title away from the creation placeholder, which it assumed was always title IS NULL. That assumption is wrong for cloud-agent-next: session-registration.ts stamps every new row with a default title (New session - <ISO timestamp>) via createSessionForCloudAgent, so the row is never NULL and the auto-generated title arriving through the ingest pipeline (applyMetadataChanges) is always dropped with Skipping agent-generated title write; title is no longer the placeholder. Cloud Agent sessions keep their New session - ... title forever unless the user manually renames them.

Fix

The correct placeholder definition already existed in this service: POST /session/:sessionId/title treats both NULL and the CLI default-title pattern (New session - ... / Child session - ..., duplicated from kilocode's isDefaultTitle) as the placeholder, with a CAS at write time.

• Extract DEFAULT_SESSION_TITLE_PATTERN / isDefaultSessionTitle from routes/api.ts into ingest/default-session-title.ts (no behavior change there).
• applyMetadataChanges now gates the agent-generated title write on isDefaultSessionTitle(currentRow.title) instead of currentRow.title === null. User-renamed titles and earlier agent-generated titles are still never overwritten; the rest of the metadata batch is unaffected.

Tests

• metadata.test.ts: new case — agent-generated title is applied over the default title stamped at creation (the cloud-agent-next shape). Existing cases (NULL placeholder applied, user-renamed skipped, rest-of-batch still applied) unchanged.
• The extracted helper remains covered by the existing POST /session/:sessionId/title tests in api.test.ts (NULL, default-pattern, and user-title cases).

Verification

Not run locally (per request); relying on CI.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Executive Summary

Reviewed the session-ingest placeholder-title fix with high confidence: the extracted isDefaultSessionTitle helper is a verbatim move from api.ts, the new gate in applyMetadataChanges runs inside the row-locked transaction (no rename race), all default-title creation sites match the regex shape, and the new test covers the cloud-agent-next creation shape while existing placeholder/rename cases remain intact.

Files Reviewed (4 files)

• services/session-ingest/src/ingest/default-session-title.ts
• services/session-ingest/src/ingest/metadata.ts
• services/session-ingest/src/ingest/metadata.test.ts
• services/session-ingest/src/routes/api.ts

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_{Review guidance: REVIEW.md from base branch main}