fix(gateway): propagate user identity through process watcher pipeline

Background process watchers (notify_on_complete, check_interval) created
synthetic SessionSource objects without user_id/user_name. While the
internal=True bypass (1d8d4f28) prevented false pairing for agent-
generated notifications, the missing identity caused:

- Garbage entries in pairing rate limiters (discord:None, telegram:None)
- 'User None' in approval messages and logs
- No user identity available for future code paths that need it

Additionally, platform messages arriving without from_user (Telegram
service messages, channel forwards, anonymous admin actions) could still
trigger false pairing because they are not internal events.

Fix:
1. Propagate user_id/user_name through the full watcher chain:
   session_context.py → gateway/run.py → terminal_tool.py →
   process_registry.py (including checkpoint persistence/recovery)

2. Add None user_id guard in _handle_message() — silently drop
   non-internal messages with no user identity instead of triggering
   the pairing flow.

Salvaged from PRs #7664 (kagura-agent, ContextVar approach),
#6540 (MestreY0d4-Uninter, tests), and #7709 (guang384, None guard).

Closes #6341, #6485, #7643
Relates to #6516, #7392

tests/gateway/test_internal_event_bypass_pairing.py

@@ -195,6 +195,105 @@ async def test_internal_event_does_not_trigger_pairing(monkeypatch, tmp_path):
     )
 
 
+@pytest.mark.asyncio
+async def test_notify_on_complete_preserves_user_identity(monkeypatch, tmp_path):
+    """Synthetic completion event should carry user_id and user_name from the watcher."""
+    import tools.process_registry as pr_module
+
+    sessions = [
+        SimpleNamespace(
+            output_buffer="done\n", exited=True, exit_code=0, command="echo test"
+        ),
+    ]
+    monkeypatch.setattr(pr_module, "process_registry", _FakeRegistry(sessions))
+
+    async def _instant_sleep(*_a, **_kw):
+        pass
+    monkeypatch.setattr(asyncio, "sleep", _instant_sleep)
+
+    runner = _build_runner(monkeypatch, tmp_path)
+    adapter = runner.adapters[Platform.DISCORD]
+
+    watcher = _watcher_dict_with_notify()
+    watcher["user_id"] = "user-42"
+    watcher["user_name"] = "alice"
+
+    await runner._run_process_watcher(watcher)
+
+    assert adapter.handle_message.await_count == 1
+    event = adapter.handle_message.await_args.args[0]
+    assert event.source.user_id == "user-42"
+    assert event.source.user_name == "alice"
+
+
+@pytest.mark.asyncio
+async def test_none_user_id_skips_pairing(monkeypatch, tmp_path):
+    """A non-internal event with user_id=None should be silently dropped."""
+    import gateway.run as gateway_run
+
+    monkeypatch.setattr(gateway_run, "_hermes_home", tmp_path)
+    (tmp_path / "config.yaml").write_text("", encoding="utf-8")
+
+    runner = GatewayRunner(GatewayConfig())
+    adapter = SimpleNamespace(send=AsyncMock())
+    runner.adapters[Platform.TELEGRAM] = adapter
+
+    source = SessionSource(
+        platform=Platform.TELEGRAM,
+        chat_id="123",
+        chat_type="dm",
+        user_id=None,
+    )
+    event = MessageEvent(
+        text="service message",
+        source=source,
+        internal=False,
+    )
+
+    result = await runner._handle_message(event)
+
+    # Should return None (dropped) and NOT send any pairing message
+    assert result is None
+    assert adapter.send.await_count == 0
+
+
+@pytest.mark.asyncio
+async def test_none_user_id_does_not_generate_pairing_code(monkeypatch, tmp_path):
+    """A message with user_id=None must never call generate_code."""
+    import gateway.run as gateway_run
+
+    monkeypatch.setattr(gateway_run, "_hermes_home", tmp_path)
+    (tmp_path / "config.yaml").write_text("", encoding="utf-8")
+
+    runner = GatewayRunner(GatewayConfig())
+    adapter = SimpleNamespace(send=AsyncMock())
+    runner.adapters[Platform.DISCORD] = adapter
+
+    generate_called = False
+    original_generate = runner.pairing_store.generate_code
+
+    def tracking_generate(*args, **kwargs):
+        nonlocal generate_called
+        generate_called = True
+        return original_generate(*args, **kwargs)
+
+    runner.pairing_store.generate_code = tracking_generate
+
+    source = SessionSource(
+        platform=Platform.DISCORD,
+        chat_id="456",
+        chat_type="dm",
+        user_id=None,
+    )
+    event = MessageEvent(text="anonymous", source=source, internal=False)
+
+    await runner._handle_message(event)
+
+    assert not generate_called, (
+        "Pairing code should NOT be generated for messages with user_id=None"
+    )
+
+
 @pytest.mark.asyncio
 async def test_non_internal_event_without_user_triggers_pairing(monkeypatch, tmp_path):
     """Verify the normal (non-internal) path still triggers pairing for unknown users."""

tests/gateway/test_session_env.py

@@ -18,6 +18,8 @@ def test_set_session_env_sets_contextvars(monkeypatch):
         chat_id="-1001",
         chat_name="Group",
         chat_type="group",
+        user_id="123456",
+        user_name="alice",
         thread_id="17585",
     )
     context = SessionContext(source=source, connected_platforms=[], home_channels={})
@@ -25,6 +27,8 @@ def test_set_session_env_sets_contextvars(monkeypatch):
     monkeypatch.delenv("HERMES_SESSION_PLATFORM", raising=False)
     monkeypatch.delenv("HERMES_SESSION_CHAT_ID", raising=False)
     monkeypatch.delenv("HERMES_SESSION_CHAT_NAME", raising=False)
+    monkeypatch.delenv("HERMES_SESSION_USER_ID", raising=False)
+    monkeypatch.delenv("HERMES_SESSION_USER_NAME", raising=False)
     monkeypatch.delenv("HERMES_SESSION_THREAD_ID", raising=False)
 
     tokens = runner._set_session_env(context)
@@ -33,6 +37,8 @@ def test_set_session_env_sets_contextvars(monkeypatch):
     assert get_session_env("HERMES_SESSION_PLATFORM") == "telegram"
     assert get_session_env("HERMES_SESSION_CHAT_ID") == "-1001"
     assert get_session_env("HERMES_SESSION_CHAT_NAME") == "Group"
+    assert get_session_env("HERMES_SESSION_USER_ID") == "123456"
+    assert get_session_env("HERMES_SESSION_USER_NAME") == "alice"
     assert get_session_env("HERMES_SESSION_THREAD_ID") == "17585"
 
     # os.environ should NOT be touched
@@ -50,6 +56,8 @@ def test_clear_session_env_restores_previous_state(monkeypatch):
     monkeypatch.delenv("HERMES_SESSION_PLATFORM", raising=False)
     monkeypatch.delenv("HERMES_SESSION_CHAT_ID", raising=False)
     monkeypatch.delenv("HERMES_SESSION_CHAT_NAME", raising=False)
+    monkeypatch.delenv("HERMES_SESSION_USER_ID", raising=False)
+    monkeypatch.delenv("HERMES_SESSION_USER_NAME", raising=False)
     monkeypatch.delenv("HERMES_SESSION_THREAD_ID", raising=False)
 
     source = SessionSource(
@@ -57,12 +65,15 @@ def test_clear_session_env_restores_previous_state(monkeypatch):
         chat_id="-1001",
         chat_name="Group",
         chat_type="group",
+        user_id="123456",
+        user_name="alice",
         thread_id="17585",
     )
     context = SessionContext(source=source, connected_platforms=[], home_channels={})
 
     tokens = runner._set_session_env(context)
     assert get_session_env("HERMES_SESSION_PLATFORM") == "telegram"
+    assert get_session_env("HERMES_SESSION_USER_ID") == "123456"
 
     runner._clear_session_env(tokens)
 
@@ -70,6 +81,8 @@ def test_clear_session_env_restores_previous_state(monkeypatch):
     assert get_session_env("HERMES_SESSION_PLATFORM") == ""
     assert get_session_env("HERMES_SESSION_CHAT_ID") == ""
     assert get_session_env("HERMES_SESSION_CHAT_NAME") == ""
+    assert get_session_env("HERMES_SESSION_USER_ID") == ""
+    assert get_session_env("HERMES_SESSION_USER_NAME") == ""
     assert get_session_env("HERMES_SESSION_THREAD_ID") == ""