A terminal panel beside an agent chat

A real shell on the chat's own connection, opened and closed like the
inspector and never beside it. The modes govern the model; what a person
types is theirs, since they hold the credential and could open the same
shell with an ssh client. The model cannot see the panel -- a button
copies the output you choose into the composer.

The session outlives the socket: closing the panel leaves a build
running, and coming back reattaches with the scrollback. Two tabs share
one shell and the smaller window decides the size. It ends on an idle
timeout, on deleting the chat, on disabling, moving or deleting the
connection, and on a restart -- which says why rather than quietly
opening a fresh shell that has lost the working directory.

The nginx template's `Connection ""` is right for SSE and fails every
WebSocket handshake, so `location /` now uses a `map $http_upgrade`;
update.sh grows a drift check for it, because the only symptom on a
stale vhost is a panel that cannot connect.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/conftest.py

@@ -80,6 +80,28 @@ def fresh_generation_registry() -> Iterator[None]:
     generation_service._TASKS.clear()
 
 
+@pytest.fixture(autouse=True)
+def fresh_terminal_registry() -> Iterator[None]:
+    """Empty the open-shell registry between tests, for the same reason.
+
+    A leaked entry holds an asyncssh connection belonging to an event loop that
+    has since closed, and the reaper task is module-level too -- one left
+    running would wake up inside the next test's loop.
+    """
+    from lembas.services.agent import terminal as terminal_service
+
+    def _clear() -> None:
+        reaper = terminal_service._REAPER
+        if reaper is not None:
+            reaper.cancel()
+        terminal_service._REAPER = None
+        terminal_service._SESSIONS.clear()
+
+    _clear()
+    yield
+    _clear()
+
+
 @pytest.fixture
 def db() -> Iterator[Session]:
     session = get_session_factory()()