release: prepare v0.1.5 manual-search recall split

[tryweb]

Summary

• Add source field to RecallEvent to distinguish system-transform (auto recall) from manual-search (user-initiated).
• memory_search now emits a recall event with source: "manual-search" and injected: false.
• EffectivenessSummary.recall gains auto/manual sub-structures and manualRescueRatio — the first instrumented proxy metric from the low-feedback evaluation framework.
• Blended top-level fields (requested, hitRate, injectionRate) are preserved for backward compatibility.

Validation

• Docker: docker compose build --no-cache && docker compose up -d && docker compose exec app npm run verify
• Foundation: 9/9 pass
• Regression: 17/17 pass (includes new recall-split test)
• Retrieval: 2/2 pass

OpenSpec

• add-manual-search-recall-split: archived, main specs synced
• add-low-feedback-memory-evaluation: archived, main specs synced