✨ Add verify skill for the agent loop

A project-local Agent Skill (.agents/skills/verify/SKILL.md) wraps the
correctness ladder as an on-demand procedure: run npm run test, recover by
fixing the root cause in the types (not by suppressing them), optionally run
whole-project npm run check, and commit through the hook. Exposed as
/skill:verify for pi, and read by any Agent-Skills harness from .agents/skills/.

It is a procedure, not a doc fork: it links AGENTS.md / CONTRIBUTING.md /
package.json instead of restating the rules, so there is no drift.

Agents must not start `npm run watch` -- it never returns and blocks the turn.
The skill's ladder drops watch and calls it out under "What not to run here";
AGENTS.md gains a matching guardrail.

.agents/skills/verify/SKILL.md

@@ -0,0 +1,40 @@
+---
+name: verify
+description: Run tiny-pattern-ts's fast, offline correctness gates — `npm run test` (mandatory type check + unit suite), then an optional whole-project `npm run check` — and recover from failures without suppressing the type system. Use when verifying TypeScript/ESM changes before committing, when asked to check or run tests, or when a pre-commit hook fails.
+---
+
+# Verify (tiny-pattern-ts)
+
+The repo's correctness ladder. `test` is the gate you are responsible for; `check` is a
+whole-project confirmation; both are fast and offline. Do not pull repo-maintenance scans
+into the feature loop.
+
+## Procedure
+
+1. `npm run test` — type check + unit suite. This is the gate.
+2. If it fails: read the error, then fix the **root cause in the types/code**. Do not
+   silence it with `@ts-nocheck` / `@ts-ignore` / `oxlint-disable` / an `as` cast (see
+   [AGENTS.md § Never do](../../../AGENTS.md#never-do)). Re-run.
+3. Optional whole-project pass: `npm run check` (`tsc → oxlint → oxfmt → cspell`).
+   Pre-commit already runs these on staged files; `check` confirms the entire tree.
+4. If `check` flags style or format: `npm run fix`, then repeat from step 1.
+5. Commit normally — the pre-commit hook re-runs the staged-file checks. Never bypass a
+   hook with `git commit --no-verify`.
+
+## What not to run here
+
+- `npm run maintain` (`maintain:knip` + `maintain:outdated`) — advisory scans, not
+  correctness. Feature work must not gate on a stale dependency or an unused export; CI
+  runs it as a non-blocking job. Run it only on an explicit maintenance / update-deps branch.
+- `npm run build` — emit is exercised by the CI publish job, not the dev loop.
+- `npm run watch` — a persistent, never-returning process (`--watch`) meant for a
+  human dev loop (stop with Ctrl-C). Never run it as an agent: it blocks the turn
+  and streams continuous output. Use `npm run test` for feedback instead.
+
+## The ladder (fastest → most thorough)
+
+pre-commit (~1.3s, staged files) → `npm run test` (~3.5s) → `npm run check` (~3s,
+whole project).
+
+Source of truth for every command: [`package.json#scripts`](../../../package.json).
+Why each tier exists: [CONTRIBUTING.md § Feedback tiers](../../../CONTRIBUTING.md#feedback-tiers).