chore(workflow): simplify agent tooling and docs

docs/workflow/agent-skills.md

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+<!-- read_when: using or modifying repo-local agent skills -->
+
+# Agent Skills
+
+Status: active
+Last verified: 2026-08-13
+Owner: Kyle Yasuda
+Read when: using, adding, or changing a repo-local agent workflow skill
+
+## Canonical Skills
+
+- `.agents/skills/subminer-change-verification/`
+  - Selects the cheapest sufficient repo-native verification lane.
+  - Defers command ownership to `package.json` and `docs/workflow/verification.md`.
+
+Repo-local workflows stay as standalone skills. Do not add plugin packaging, marketplace metadata, or compatibility shims unless the workflow is intentionally being distributed beyond this repository.
+
+## Rules
+
+- Keep each skill focused on one repeatable repository task.
+- Prefer instructions over helper scripts unless deterministic tooling provides clear value beyond existing package commands.
+- Keep trigger descriptions narrow enough to avoid invoking skills for unrelated requests.
+- Update this page and the documentation catalog when skill ownership changes.
+
+## Verification
+
+For skill or internal workflow documentation changes, run:
+
+```bash
+bun run test:docs:kb
+```