fix: reap zombie subprocesses in web_server action status and meet_bot cleanup

- web_server.py: after proc.poll() returns a non-None exit code, call
  proc.wait() to reap the child and move the entry from _ACTION_PROCS
  to _ACTION_RESULTS. Previously .poll() alone left <defunct> zombies.
- meet_bot.py: terminate and wait on the pcm_pump subprocess (paplay/
  ffmpeg) during the finally-block teardown. Previously leaked on every
  normal bot exit.
- tests: add test_action_status_reaps_completed_process and
  test_action_status_ignores_wait_failure covering both the happy path
  and the wait()-raises-OSError edge case.

Closes #38032

hermes_cli/web_server.py

@@ -1691,6 +1691,13 @@ async def get_action_status(name: str, lines: int = 200):
         exit_code = proc.poll()
         running = exit_code is None
         pid = proc.pid
+        if exit_code is not None:
+            try:
+                proc.wait(timeout=1)
+            except Exception:
+                pass
+            _ACTION_RESULTS[name] = {"exit_code": exit_code, "pid": pid}
+            _ACTION_PROCS.pop(name, None)
 
     return {
         "name": name,