Add Xorg Remote controller capture with a core F11 escape

The Xorg command owner gains an exclusive Remote capture mode. Native
transitions pass through the repeat normalizer and capture router;
forwarded keys leave as remote.input events, Remote's own shortcuts are
dispatched locally, and F11 ends capture on the X thread. Reader policy,
overflow or inconsistent input also end it. Ending releases forwarded
keys first and keeps the grab until held keys are released. Local key
echo is suppressed during capture. The app attaches the owner to
sessions installed with keyboard-capture.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/native_remote_input.py

@@ -395,7 +395,7 @@ def main():
         # paths as well as the standalone recovery experiment.
         subprocess.run([
             "go", "test", "-race", "./internal/platform/xorg", "-count=1", "-timeout=60s",
-            "-run", "^TestNative(InternalUICapturesAndReleases|LearnModeKeepsKeysFromFocusedApplication|RemoteInjectedKeyObservation|RemoteRepeatNormalizesHeldKey|LocalUIRejectsInjectedApproval|SuspendedQueuedKey|XTermHandoffKeepsKeypadReleased)$",
+            "-run", "^TestNative(InternalUICapturesAndReleases|LearnModeKeepsKeysFromFocusedApplication|RemoteInjectedKeyObservation|RemoteRepeatNormalizesHeldKey|RemoteCaptureForwardsBypassesAndEscapes|LocalUIRejectsInjectedApproval|SuspendedQueuedKey|XTermHandoffKeepsKeypadReleased)$",
             "-v"], cwd=Path(__file__).resolve().parents[1], check=True,
             env=dict(os.environ, CTHULHU_NATIVE_X11="1", CTHULHU_NATIVE_REMOTE_INPUT="1"))
     else: