fix(picker): remove max_models=50 cap in interactive model pickers

The interactive model pickers (Desktop REST API, TUI model.options, CLI
/model) were hard-capped at max_models=50, which truncated large provider
catalogs like Kilo Gateway (336 models) to just 50 entries. This made
most models undiscoverable via the picker search box.

Changes:
- Change build_models_payload() default from max_models=50 to None (unlimited)
- Change list_authenticated_providers() default from max_models=8 to None
- Change list_picker_providers() default from max_models=8 to None
- Fix all [:max_models] slicing to handle None as 'no limit'
- Remove max_models=50 from 5 interactive picker callers:
  * web_server.py: get_model_options (Desktop /api/model/options)
  * web_server.py: get_recommended_default_model
  * model_switch.py: prewarm_picker_cache_async
  * tui_gateway/server.py: model.options JSON-RPC
  * cli.py: HermesCLI model picker
- Telegram/Discord inline keyboard picker (gateway/slash_commands.py)
  still passes max_models=50 explicitly — unchanged behavior.

The total_models field was already in the response payload and is now
meaningful since models.length == total_models for interactive pickers.

Fixes #48279

hermes_cli/web_server.py

@@ -3323,7 +3323,6 @@ def get_model_options(profile: Optional[str] = None):
         with _profile_scope(profile):
             return build_models_payload(
                 load_picker_context(),
-                max_models=50,
                 include_unconfigured=True,
                 picker_hints=True,
                 canonical_order=True,
@@ -3398,7 +3397,7 @@ def get_recommended_default_model(provider: str = ""):
     try:
         from hermes_cli.inventory import build_models_payload, load_picker_context
 
-        payload = build_models_payload(load_picker_context(), max_models=50)
+        payload = build_models_payload(load_picker_context())
         for row in payload.get("providers", []):
             if str(row.get("slug", "")).lower() == slug:
                 models = row.get("models") or []