test(tui): fix stale mocks + xdist flakes in TUI test suite

All 61 TUI-related tests green across 3 consecutive xdist runs.

tests/tui_gateway/test_protocol.py:
- rename `get_messages` → `get_messages_as_conversation` on mock DB (method
  was renamed in the real backend, test was still stubbing the old name)
- update tool-message shape expectation: `{role, name, context}` matches
  current `_history_to_messages` output, not the legacy `{role, text}`

tests/hermes_cli/test_tui_resume_flow.py:
- `cmd_chat` grew a first-run provider-gate that bailed to "Run: hermes
  setup" before `_launch_tui` was ever reached; 3 tests stubbed
  `_resolve_last_session` + `_launch_tui` but not the gate
- factored a `main_mod` fixture that stubs `_has_any_provider_configured`,
  reused by all three tests

tests/test_tui_gateway_server.py:
- `test_config_set_personality_resets_history_and_returns_info` was flaky
  under xdist because the real `_write_config_key` touches
  `~/.hermes/config.yaml`, racing with any other worker that writes
  config. Stub it in the test.

tests/test_tui_gateway_server.py

@@ -231,6 +231,9 @@ def test_config_set_personality_resets_history_and_returns_info(monkeypatch):
     monkeypatch.setattr(server, "_session_info", lambda agent: {"model": getattr(agent, "model", "?")})
     monkeypatch.setattr(server, "_restart_slash_worker", lambda session: None)
     monkeypatch.setattr(server, "_emit", lambda *args: emits.append(args))
+    # _write_config_key writes to ~/.hermes/config.yaml — races with other
+    # xdist workers that touch the same file. Stub it out.
+    monkeypatch.setattr(server, "_write_config_key", lambda path, value: None)
 
     resp = server.handle_request(
         {"id": "1", "method": "config.set", "params": {"session_id": "sid", "key": "personality", "value": "helpful"}}