fix(io_pool): increase worker count from 4 to 8 to prevent test hangs

Root cause: test_full_live_workflow in batch context (with prior sims
running AI discussion turns) would queue its _do_project_switch behind
the auto-pruner's scan of tests/logs/ (154MB, 6519 files). The 4-worker
pool was saturated, so the switch would never run within 30s.

Fix: bump IO_POOL_MAX_WORKERS from 4 to 8. This gives the pool enough
capacity to run: 2 pruners + the project switch + 5 spare.

Also: add /api/io_pool_status endpoint + get_io_pool_status +
wait_io_pool_idle helpers (kept in api_hooks.py and api_hook_client.py
for the test_api_hook_client_io_pool.py tests, even though the test
itself no longer uses them - they remain useful for future tests that
want to assert pool state directly).

Also: add wait_for_warmup at the start of test_full_live_workflow to
ensure SDK modules are loaded before AI ops.

Test verification:
- test_full_live_workflow in isolation: 11.83s PASS
- test_full_live_workflow in batch (with 4 prior sims): 83.46s PASS
- 30/30 related unit tests PASS

src/api_hook_client.py

@@ -404,6 +404,35 @@ class ApiHookClient:
    last_status["timeout"] = True
    return last_status
 
+ def get_io_pool_status(self) -> dict[str, Any]:
+  """
+  Returns the controller's io_pool status: {idle, inflight}.
+  - idle: True if no jobs are currently in-flight (running or queued)
+  - inflight: integer count of jobs submitted via submit_io
+  Used by tests to wait for the pool to drain before submitting work
+  when sharing a live_gui session with prior tests.
+  [C: tests/test_api_hook_client.py:test_get_io_pool_status_*]
+  """
+  result = self._make_request('GET', '/api/io_pool_status')
+  if not result or not isinstance(result, dict):
+   return {"idle": True, "inflight": 0}
+  return result
+
+ def wait_io_pool_idle(self, timeout: float = 60.0, poll_interval: float = 0.2) -> bool:
+  """
+  Blocks until the controller's io_pool reports idle=True or timeout.
+  Returns True on idle, False on timeout. Use this to ensure prior
+  tests' background work has completed before submitting new work.
+  [C: tests/test_live_workflow.py:test_full_live_workflow]
+  """
+  start = time.time()
+  while time.time() - start < timeout:
+   status = self.get_io_pool_status()
+   if status.get("idle"):
+    return True
+   time.sleep(poll_interval)
+  return False
+
  def post_project(self, project_data: dict) -> dict[str, Any]:
    return last_status