voice-limit-guard: live revoke never fired — LiveKit's JSON uses snake_case permissions

livekit-server (verified on 1.13.7) serialises ParticipantPermission as
can_publish / can_publish_sources; the reconciler read canPublish /
canPublishSources, saw 'publishes nothing' for everyone and never called
UpdateParticipant, so turning Allow Screen Sharing off did not stop an
in-progress share. Normalise the permission keys before deciding.
Verified on a local Synapse + LiveKit + guard stack: share track gone
from the SFU 2 s after the policy flip. Tests added (44 pass).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

livekit/test_voice_limit_guard.py

@@ -362,3 +362,30 @@ class TestRoomStateParsing(unittest.TestCase):
 
 if __name__ == "__main__":
     unittest.main()
+
+
+class NormalizePermissionTest(unittest.TestCase):
+    """livekit-server's JSON uses proto names (snake_case); the reconciler must
+    not read camelCase and conclude nobody publishes (which silently disabled
+    the live screenshare kill)."""
+
+    def test_snake_case_permission_is_reconciled(self):
+        calls = []
+        guard.livekit_update_participant = lambda alias, identity, perm: calls.append((identity, perm))
+        participant = {
+            "identity": "@a:x:DEV",
+            "permission": {"can_subscribe": True, "can_publish": True, "can_publish_data": True, "can_publish_sources": []},
+        }
+        changed = guard.reconcile_participant("!r:x", participant, {"SCREEN_SHARE", "SCREEN_SHARE_AUDIO"})
+        self.assertTrue(changed)
+        identity, perm = calls[0]
+        self.assertEqual(identity, "@a:x:DEV")
+        self.assertTrue(perm["canPublish"])
+        self.assertNotIn("SCREEN_SHARE", perm["canPublishSources"])
+        self.assertIn("MICROPHONE", perm["canPublishSources"])
+        self.assertTrue(perm["canSubscribe"])  # preserved
+
+    def test_camel_case_still_works(self):
+        guard.livekit_update_participant = lambda *a: None
+        participant = {"identity": "@a:x:DEV", "permission": {"canPublish": True, "canPublishSources": ["CAMERA"]}}
+        self.assertFalse(guard.reconcile_participant("!r:x", participant, {"SCREEN_SHARE"}))