Poll for readiness in test_multiprocess_health_check and run_server

Apply the same polling pattern to `test_multiprocess_health_check` — wait
for all processes to be alive instead of a fixed 1s sleep.

In `run_server`, wait for `server.started` instead of a fixed 0.1s sleep
to avoid connection races on slow setups (e.g. free-threaded Python 3.14).

tests/supervisors/test_multiprocess.py

@@ -84,7 +84,11 @@ def test_multiprocess_health_check() -> None:
     process = supervisor.processes[0]
     process.kill()
     assert not process.is_alive()
-    time.sleep(1)
+    deadline = time.monotonic() + 10
+    while time.monotonic() < deadline:
+        if all(p.is_alive() for p in supervisor.processes):
+            break
+        time.sleep(0.1)
     for p in supervisor.processes:
         assert p.is_alive()
     supervisor.signal_queue.append(signal.SIGINT)

tests/utils.py

@@ -16,7 +16,8 @@ from uvicorn import Config, Server
 async def run_server(config: Config, sockets: list[socket] | None = None) -> AsyncIterator[Server]:
     server = Server(config=config)
     task = asyncio.create_task(server.serve(sockets=sockets))
-    await asyncio.sleep(0.1)
+    while not server.started:
+        await asyncio.sleep(0.05)
     try:
         yield server
     finally: