ControlModeEngine(types): Extend process protocol (pid/poll)

why: mypy flagged pid/poll usage and FakeProcess stubs; protocol needs those attributes.

what:
- Add pid and poll to _ControlProcess protocol to match Popen/fakes
- Update test fakes to implement protocol directly (no casts)
- Keep ruff/mypy clean without ignores

Author: tony

src/libtmux/_internal/engines/control_mode.py

@@ -34,13 +34,16 @@ class _ControlProcess(t.Protocol):
     stdin: t.TextIO | None
     stdout: t.Iterable[str] | None
     stderr: t.Iterable[str] | None
+    pid: int | None
 
     def terminate(self) -> None: ...
 
     def kill(self) -> None: ...
 
     def wait(self, timeout: float | None = None) -> t.Any: ...
 
+    def poll(self) -> int | None: ...
+
 
 class _ProcessFactory(t.Protocol):
     """Protocol for constructing a control-mode process."""

tests/test_control_mode_engine.py

@@ -4,7 +4,6 @@
 
 import io
 import pathlib
-import subprocess
 import time
 import typing as t
 
@@ -86,6 +85,7 @@ def __init__(self) -> None:
             self.stdout = BlockingStdout()
             self.stderr = None
             self._terminated = False
+            self.pid = 1234
 
         def terminate(self) -> None:  # pragma: no cover - simple stub
             self._terminated = True
@@ -96,14 +96,17 @@ def kill(self) -> None:  # pragma: no cover - simple stub
         def wait(self, timeout: float | None = None) -> None:  # pragma: no cover
             return None
 
+        def poll(self) -> int | None:  # pragma: no cover - simple stub
+            return 0
+
     engine = ControlModeEngine(command_timeout=0.01)
 
     fake_process = FakeProcess()
 
     def fake_start(server_args: t.Sequence[str | int] | None) -> None:
         engine.tmux_bin = "tmux"
         engine._server_args = tuple(server_args or ())
-        engine.process = t.cast(subprocess.Popen[str], fake_process)
+        engine.process = fake_process
 
     monkeypatch.setattr(engine, "_start_process", fake_start)
 
@@ -122,6 +125,7 @@ def __init__(self) -> None:
             self.stdout: t.Iterator[str] = iter([])  # no output
             self.stderr = None
             self._terminated = False
+            self.pid = 5678
 
         def terminate(self) -> None:
             self._terminated = True
@@ -132,12 +136,15 @@ def kill(self) -> None:
         def wait(self, timeout: float | None = None) -> None:
             return None
 
+        def poll(self) -> int | None:
+            return 0
+
     engine = ControlModeEngine(command_timeout=5.0)
 
     def fake_start(server_args: t.Sequence[str | int] | None) -> None:
         engine.tmux_bin = "tmux"
         engine._server_args = tuple(server_args or ())
-        engine.process = t.cast(subprocess.Popen[str], FakeProcess())
+        engine.process = FakeProcess()
 
     monkeypatch.setattr(engine, "_start_process", fake_start)
 
@@ -243,6 +250,7 @@ class FakeProcess:
         def __init__(self) -> None:
             self.stdin = FakeStdin()
             self._terminated = False
+            self.pid = 9999
 
         def terminate(self) -> None:
             self._terminated = True
@@ -253,8 +261,11 @@ def kill(self) -> None:  # pragma: no cover - simple stub
         def wait(self, timeout: float | None = None) -> None:
             return None
 
+        def poll(self) -> int | None:
+            return 0
+
     engine = ControlModeEngine()
-    engine.process = FakeProcess()  # type: ignore[assignment]
+    engine.process = FakeProcess()
 
     with pytest.raises(case.should_raise):
         engine._write_line("list-sessions", server_args=())