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_hooks.py

@@ -134,6 +134,17 @@ class HookHandler(BaseHTTPRequestHandler):
       "error": getattr(controller, "_project_switch_error", None),
      }
     self.wfile.write(json.dumps(payload).encode("utf-8"))
+   elif self.path == "/api/io_pool_status":
+    self.send_response(200)
+    self.send_header("Content-Type", "application/json")
+    self.end_headers()
+    controller = _get_app_attr(app, "controller", None)
+    if controller is None:
+     payload = {"idle": True, "inflight": 0}
+    else:
+     inflight = getattr(controller, "_io_pool_inflight", 0)
+     payload = {"idle": inflight == 0, "inflight": inflight}
+    self.wfile.write(json.dumps(payload).encode("utf-8"))
    elif self.path == "/api/session":
     self.send_response(200)
     self.send_header("Content-Type", "application/json")