📝 Move knip + outdated to a maintain: prefix

`npm run check` should be the fast, offline correctness ladder only (tsc +
oxlint + oxfmt + cspell, ~3s), so an agent can run it as a confirmation gate
during feature work. check:knip / check:outdated were advisory whole-project /
network scans, and check-outdated exits non-zero whenever any dep is behind.
Keeping them in check made `npm run check` (and the CI build gate) fail on
dependency freshness, which must not block an unrelated feature PR.

Rename them to maintain:knip / maintain:outdated, aggregate under `npm run
maintain`, and run it in CI as a dedicated non-blocking job (continue-on-error)
that surfaces findings without ever gating a merge. Update the script-prefix
convention, the feedback-tier table, and AGENTS.md: the agent may now run
`npm run check`; only `maintain` stays out of the feature loop.

AGENTS.md

@@ -10,12 +10,16 @@ first-action facts. Do not restate evolving prose here — it will drift.
 - Project: F#-style pattern matching for TypeScript/ESM. Node `>=26` (pinned via `.node-version`), ESM-only (no CommonJS shim).
 - **Mandatory while iterating:** `npm run test` (runs `check:tsc`, then the unit suite). This is the gate you are responsible for.
 - **On commit:** write a good message (see [CONTRIBUTING.md § Commit messages](./CONTRIBUTING.md#commit-messages)). Lefthook's pre-commit hook already runs the fast, offline, staged-file checks (`tsc` + `oxlint` + `oxfmt` + `cspell`) — don't run them by hand. If the hook fails on style, `npm run fix`, restage, recommit.
-- **`npm run check` is NOT part of the feature loop.** It adds `knip` (dead-code/deps) and `check:outdated` (registry) — repo-maintenance scans. Run it only on an explicit maintenance / update-deps branch; CI runs it on the PR regardless.
+- **Optional final gate:** `npm run check` (the fast, offline, whole-project correctness ladder: `tsc → oxlint → oxfmt → cspell`). Safe to run whenever you want a project-wide confirmation; pre-commit already covers staged files.
+- **`npm run maintain` is NOT part of the feature loop.** `maintain:knip` (dead-code/deps) and `maintain:outdated` (registry) are advisory maintenance scans. Run them only on an explicit maintenance / update-deps branch; CI surfaces them via a non-blocking job, never as a gate.
 
     ```sh
-    npm run test   # the bot's definition of done; commit normally after
+    npm run test    # mandatory gate
+    npm run check   # optional project-wide confirmation
     ```
 
+    The bot's definition of done: `npm run test` green, commit normally after.
+
 ## Never do
 
 Don't silence the type system to force a green run. As an agent these are forbidden: