feat: mirror reflection slice rows into the daily memory journal

[gorkem2020]

The mdMirror daily journal (memory/<date>.md) mirrors writer-1 reflection mapped rows, smart-extraction rows, and manual memory_store rows, but not the reflection writer-2 slice rows (storeReflectionToLanceDB's event / invariant / derived rows). Those rows entered the database invisibly; the daily file only got the "Reflection generated: <path>" pointer line. This PR closes that gap so every row that enters the database is observable in the daily file without CLI tools.

• storeReflectionToLanceDB (src/reflection-store.ts) gains an optional onPersisted(entry, kind) hook, fired after each event / item-invariant / item-derived row is stored. The combined-legacy row is intentionally excluded since it is out of scope for this change (it is a distinct legacy row type, not one of the writer-2 slice rows this PR targets).
• Callback failures are swallowed with a try/catch so a mirror bug can never abort reflection persistence, matching the existing SmartExtractor.notifyPersisted convention for the same kind of hook.
• index.ts wires mdMirror through this hook with source labels reflection-slice:event, reflection-slice:invariant, and reflection-slice:derived.
• The event row's text is a multi-line key=value block. It renders as one line for free, because createMdMirrorWriter's existing line formatter already replaces \n with a space before appending to the daily file - no changes were needed there.

Test plan

• Red-first: added tests to test/memory-reflection.test.mjs asserting onPersisted fires for event/invariant/derived rows, is skipped for the legacy row, does not break storage when absent, does not abort remaining stores if it throws, and that the event row's multi-line text collapses to one line under the existing mirror formatting contract. All five failed before the implementation and pass after.
• npm run build (tsc) clean.
• Full local npm test chain green (one test skipped: a known host-side port 11434 conflict unrelated to this change).

Notes for reviewers

While working on this I found that test/memory-reflection.test.mjs itself (the file with the most direct coverage of storeReflectionToLanceDB) is not wired into either package.json's test script or scripts/ci-test-manifest.mjs on master, and separately has four pre-existing failing tests unrelated to this change. Both are out of scope here and are called out separately rather than folded into this PR.