[hkrlogic]

Tightens how agent writes (create_item, update_item) are checked against the library schema.

1. Labels normalized like the UI (trim, lower case, dedupe) on every write. Migration 024_normalize_labels.sql backfills items.labels, published_snapshot.labels and previous_published_snapshot.labels; the published_version / review_by triggers are paused for the backfill so it does not count as a new publish. Over-long labels are refused, not truncated.
2. No silent drops: non-string / non-string-array values are refused with the key names (null = not sent). summary on a plain General library is refused over MCP (internal callers unchanged).
3. Optional version fields must match 1, 1.0, 1.0.2 when non-empty.
4. Single source for default per-type max (src/items/field-limits.ts) used by the tool schema, save check and field/table/custom proposals. Fixes text default 200 (tool) vs 8,000 (save).
5. All validation issues returned at once; humanItemMessage keeps unknown-field wording and the rest.

Tests: test/write-validation.test.ts (11 tests incl. migration). Docs: concepts.md (how writes are checked), CHANGELOG.