mcp: add hs-test server for hyperscript conformance runs

Wraps `node tests/hs-run-filtered.js` so the agent can run/filter/kill
test runs without per-call Bash permission prompts. Tools:

- hs_test_run: run the suite (optional suite filter, start/end range,
  step_limit, verbose); enforces a wall-clock timeout via SIGTERM/SIGKILL
  on the child process group, so a hung CEK loop can't strand the agent.
- hs_test_kill: SIGTERM/SIGKILL any background runner.
- hs_test_regen: regenerate spec/tests/test-hyperscript-behavioral.sx.
- hs_test_status: list any in-flight runners.

Stdio JSON-RPC, same protocol as tools/mcp_services.py.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.mcp.json

@@ -8,6 +8,11 @@
       "type": "stdio",
       "command": "python3",
       "args": ["tools/mcp_services.py"]
+    },
+    "hs-test": {
+      "type": "stdio",
+      "command": "python3",
+      "args": ["tools/mcp_hs_test.py"]
     }
   }
 }