fix(pty-bridge): terminate PTY process groups on teardown

hermes_cli/pty_bridge.py

@@ -250,13 +250,23 @@ class PtyBridge:
             return
         self._closed = True
 
+        try:
+            pgid = os.getpgid(self._proc.pid)
+        except Exception:
+            pgid = None
+
         # SIGHUP is the conventional "your terminal went away" signal.
-        # We escalate if the child ignores it.
+        # Send it to the whole foreground process group, not just the PTY
+        # leader: the dashboard TUI starts helper children such as the Python
+        # slash worker, and killing only the leader can strand those helpers.
         for sig in (signal.SIGHUP, signal.SIGTERM, signal.SIGKILL):  # windows-footgun: ok — POSIX-only module (imports fcntl/termios/ptyprocess at top)
             if not self._proc.isalive():
                 break
             try:
-                self._proc.kill(sig)
+                if pgid is not None:
+                    os.killpg(pgid, sig)
+                else:
+                    self._proc.kill(sig)
             except Exception:
                 pass
             deadline = time.monotonic() + 0.5