feat: add local agent runtime loop

docs/m4-agent-loop.md

@@ -10,11 +10,39 @@ This check stays local. It uses the `internal/agent` runtime skeleton and a
 repo fixture to verify:
 
 - lifecycle coverage for `create`, `start`, `trace`, `finish`, and `cleanup`;
+- manager `create/status/trace/evidence/cleanup` contract behavior through the
+  local file-system runtime;
+- worker `dry-run` task claim, trace write, evidence write, and temporary
+  workspace cleanup;
 - workspace isolation per agent session;
-- explicit skills `commitId` wiring;
+- explicit skills `commitId` and `version` wiring;
 - evidence record fields, URI shape, and SHA-256 digest;
 - the fixture evidence note that marks the run as local-only.
 
+The local CLI contract is JSON-only and short-lived:
+
+```sh
+STATE_DIR="$(mktemp -d)"
+node cmd/hwlab-agent-mgr/main.mjs create --state-dir "$STATE_DIR" \
+  --agent-session-id agt_local_m4 --project-id prj_local_m4 \
+  --goal "verify local agent loop" --prompt "dry-run" \
+  --skill-commit-id 6509a35 --skill-version v1
+node cmd/hwlab-agent-worker/main.mjs dry-run --state-dir "$STATE_DIR" \
+  --agent-session-id agt_local_m4 \
+  --skill-commit-id 6509a35 --skill-version v1
+node cmd/hwlab-agent-mgr/main.mjs status --state-dir "$STATE_DIR" \
+  --agent-session-id agt_local_m4
+node cmd/hwlab-agent-mgr/main.mjs trace --state-dir "$STATE_DIR" \
+  --agent-session-id agt_local_m4
+node cmd/hwlab-agent-mgr/main.mjs evidence --state-dir "$STATE_DIR" \
+  --agent-session-id agt_local_m4
+node cmd/hwlab-agent-mgr/main.mjs cleanup --state-dir "$STATE_DIR" \
+  --agent-session-id agt_local_m4
+```
+
+If either skills `commitId` or `version` is omitted, health and evidence are
+reported as `degraded`; no fallback commit or external skill source is inferred.
+
 ## Real DEV Preconditions
 
 A real DEV M4 run is separate from this smoke. It would need a live DEV