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.

apps/desktop/src/app/session/hooks/use-session-actions.ts

@@ -331,7 +331,14 @@ export function useSessionActions({
         // so single-profile users are unaffected).
         await ensureGatewayProfile($newChatProfile.get())
         const cwd = $currentCwd.get().trim() || getRememberedWorkspaceCwd()
-        const created = await requestGateway<SessionCreateResponse>('session.create', { cols: 96, ...(cwd && { cwd }) })
+        // Pass the owning profile so a new chat under a non-launch profile (global
+        // remote mode) builds its agent + persists against THAT profile's home/db.
+        const newChatProfile = $newChatProfile.get()
+        const created = await requestGateway<SessionCreateResponse>('session.create', {
+          cols: 96,
+          ...(cwd && { cwd }),
+          ...(newChatProfile ? { profile: newChatProfile } : {})
+        })
         const stored = created.stored_session_id ?? null
 
         if (