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>

src/lembas/api/agents.py

@@ -25,6 +25,7 @@ from lembas.api.pages import sidebar_context
 from lembas.db.models import AUTH_METHODS, AUTH_PASSWORD, SshProfile
 from lembas.services import settings_store
 from lembas.services.agent import ssh as ssh_service
+from lembas.services.agent import terminal as terminal_service
 from lembas.services.agent.base import ExecError
 from lembas.services.crypto import UNCHANGED_SENTINEL, decrypt, keep_or_replace, mask
 from lembas.web.templating import render
@@ -293,6 +294,9 @@ async def forget_host_key(request: Request, db: Db, user: RequiredUser, profile_
     profile = _profile(db, user, profile_id)
     profile.host_key = ""
     profile.host_fingerprint = ""
+    # Un-trusting a host has to reach the shell already open on it, or the one
+    # connection that matters is the one this does not touch.
+    await terminal_service.close_for_profile(profile.id)
     db.commit()
     return render(request, "agents/_check.html", {"profile": profile, "forgotten": True})
 
@@ -301,6 +305,7 @@ async def forget_host_key(request: Request, db: Db, user: RequiredUser, profile_
 async def delete_profile(db: Db, user: RequiredUser, profile_id: str) -> Response:
     profile = _profile(db, user, profile_id)
     name = profile.name
+    await terminal_service.close_for_profile(profile.id)
     db.delete(profile)
     db.commit()
     log.info("%s deleted ssh profile %s", user.email, name)
@@ -342,6 +347,13 @@ async def update_profile(request: Request, db: Db, user: RequiredUser, profile_i
         profile.host_fingerprint = ""
         log.info("%s moved ssh profile %s; its host key was forgotten", user.email, profile.name)
 
+    # A shell already open holds its own connection and would not notice any of
+    # this. `session.profile_for` re-checks the profile on every reply, so the
+    # model stops at once; without the line below, "I disabled that connection"
+    # would simply not be true of the terminal on screen.
+    if not profile.enabled or not profile.host_key or (profile.host, profile.port) != before:
+        await terminal_service.close_for_profile(profile.id)
+
     db.commit()
     return RedirectResponse(
         f"/agents/{profile.id}?saved=Saved.", status_code=status.HTTP_303_SEE_OTHER