* fix(#2202): preserve unknown frontmatter keys in syncStateFrontmatter
syncStateFrontmatter rebuilds frontmatter from a fixed schema, dropping any
custom/unknown key on every mutating verb. Before reconstruction, merge any
existing frontmatter key the schema does not own. Schema keys still win.
Closes#2202
* docs(#2202): add changeset fragment
* docs(#2202): backfill PR number
* fix(#2202): add regression test + remove redundant type assertion
- tests/state.test.cjs: behavioral regression test asserting custom/unknown
STATE.md frontmatter keys survive a mutating verb (they were silently dropped
before the syncStateFrontmatter carry-forward).
- src/state.cts: drop the unnecessary `as Record<string, unknown>` assertion
that tripped @typescript-eslint/no-unnecessary-type-assertion (the lint-tests
gate failure).
Refs #2202
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---------
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
