fix(gateway): new chats honor their profile in global-remote mode (#39993)

Follow-up to #39921. That PR scoped session.resume + prompt.submit to a
session's profile, but a BRAND-NEW chat (session.create) under a non-launch
profile was still built and persisted against the dashboard's launch profile.
Two visible symptoms in app-global remote mode (one dashboard, many profiles):

  1. "who are you" in profile S replied as the launch (default) profile/agent —
     the agent was built with the launch HERMES_HOME, so config/SOUL/identity
     came from the wrong profile.
  2. "session not found" on later resume — _ensure_session_db_row persisted the
     row into the launch profile's state.db via _get_db(), so the session lived
     in the wrong db, the unified list mis-tagged it (it showed up under BOTH
     profiles), and resume routed to the wrong one.

Fix — carry the owning profile through the create path too:

- session.create accepts an optional `profile`; resolves its home and stores
  `profile_home` on the session (alongside what resume already set).
- _start_agent_build binds that profile's HERMES_HOME while building the agent
  (config/skills/model/identity resolve to it) and hands the agent the profile's
  state.db so turns persist there.
- _ensure_session_db_row writes the row into the profile's state.db, not the
  launch db — fixing the duplicate row + mis-tag + resume 404.
- desktop sends the new-chat profile on session.create.

None/launch profile → unchanged (single-profile and per-profile-remote setups
take the same path). Verified live against a one-dashboard / multi-profile
remote: a new chat under `work` builds as work's agent (correct SOUL identity),
persists ONLY to work's state.db (launch db stays empty), the unified list tags
it `work` exactly once, and it resumes cleanly.

tests/test_tui_gateway_server.py: _make_agent mocks updated for the session_db
param added in #39921's build path.

tests/test_tui_gateway_server.py

@@ -3577,7 +3577,7 @@ def test_session_create_close_race_does_not_orphan_worker(monkeypatch):
     release_build = threading.Event()
     build_entered = threading.Event()
 
-    def _slow_make_agent(sid, key, session_id=None):
+    def _slow_make_agent(sid, key, session_id=None, session_db=None):
         build_started.set()
         build_entered.set()
         release_build.wait(timeout=3.0)
@@ -3685,7 +3685,7 @@ def test_session_create_no_race_keeps_worker_alive(monkeypatch):
             self.base_url = ""
             self.api_key = ""
 
-    monkeypatch.setattr(server, "_make_agent", lambda sid, key: _FakeAgent())
+    monkeypatch.setattr(server, "_make_agent", lambda sid, key, session_db=None: _FakeAgent())
     monkeypatch.setattr(server, "_SlashWorker", _FakeWorker)
     monkeypatch.setattr(
         server,
@@ -3769,7 +3769,7 @@ def test_session_create_continues_when_state_db_is_unavailable(monkeypatch):
 
     emits = []
 
-    monkeypatch.setattr(server, "_make_agent", lambda sid, key: _FakeAgent())
+    monkeypatch.setattr(server, "_make_agent", lambda sid, key, session_db=None: _FakeAgent())
     monkeypatch.setattr(server, "_SlashWorker", _FakeWorker)
     monkeypatch.setattr(server, "_get_db", lambda: None)
     monkeypatch.setattr(server, "_session_info", lambda _a, *a2: {"model": "x"})