Memory Manifest

Per-slug sync manifest + a rolled-up version. omicos-core diffs this against its local manifest.json and only re-pulls slugs whose meta_version changed (a metadata-only flip re-pulls even when the body hash is unchanged).

MUST include ALL non-deleted rows — active AND invalidated — so core never garbage-collects a superseded note's local .md (supersession is expire-don't-delete; only an explicit DELETE removes a slug).

Degrades on DB failure (last-good / 503) instead of 500-storming the most-polled endpoint (the 2026-06-24 cascade).