fix(tui): sync inference model after switches

- keep HERMES_INFERENCE_MODEL aligned with HERMES_MODEL after in-TUI model switches
- clarify static provider detection remapping docs

tests/test_tui_gateway_server.py

@@ -562,6 +562,8 @@ def test_config_set_model_syncs_tui_provider_env(monkeypatch):
 
         assert resp["result"]["value"] == "anthropic/claude-sonnet-4.6"
         assert os.environ["HERMES_TUI_PROVIDER"] == "anthropic"
+        assert os.environ["HERMES_MODEL"] == "anthropic/claude-sonnet-4.6"
+        assert os.environ["HERMES_INFERENCE_MODEL"] == "anthropic/claude-sonnet-4.6"
     finally:
         server._sessions.clear()