fix(tui): pass user_providers as dict to match CLI model-switch pipeline

The TUI's _apply_model_switch() was converting the config.yaml
`providers:` dict into a list of dicts before passing it to
switch_model(). This caused resolve_provider_full() →
resolve_user_provider() to fail, since that function expects a dict
and does `user_config.get(name)` to look up provider entries.

The result: user-defined providers (e.g. ollama) appeared in CLI's
/model picker but were invisible in the TUI.

Fix:
- tui_gateway/server.py: pass cfg.get('providers') directly (dict),
  matching what cli.py already does at line 5598.
- hermes_cli/model_switch.py: fix the validation-override block
  (line ~893) which iterated user_providers as a list — now correctly
  handles the dict format with support for both dict-keyed and
  list-format models arrays.

tui_gateway/server.py

@@ -1078,9 +1078,7 @@ def _apply_model_switch(sid: str, session: dict, raw_input: str) -> dict:
         from hermes_cli.config import get_compatible_custom_providers, load_config
 
         cfg = load_config()
-        user_provs = [
-            {"provider": k, **v} for k, v in (cfg.get("providers") or {}).items()
-        ]
+        user_provs = cfg.get("providers")
         custom_provs = get_compatible_custom_providers(cfg)
     except Exception:
         pass