refactor: single-owner model switch parsing + effective-model resolution (kills the api_server/run.py divergence class)

cli.py

@@ -9057,7 +9057,7 @@ class HermesCLI(CLIAgentSetupMixin, CLICommandsMixin, CLIBillingMixin):
         """
         from hermes_cli.model_switch import (
             switch_model,
-            parse_model_flags_detailed,
+            parse_model_switch_args,
             resolve_persist_behavior,
         )
         from hermes_cli.providers import get_label
@@ -9067,18 +9067,17 @@ class HermesCLI(CLIAgentSetupMixin, CLICommandsMixin, CLIBillingMixin):
         raw_args = parts[1].strip() if len(parts) > 1 else ""
 
         # Parse --provider, --global, --session, --once, and --refresh flags
-        parsed_flags = parse_model_flags_detailed(raw_args)
-        model_input = parsed_flags.model_input
-        explicit_provider = parsed_flags.explicit_provider
-        is_global_flag = parsed_flags.is_global
-        force_refresh = parsed_flags.force_refresh
-        is_session = parsed_flags.is_session
-        one_turn = parsed_flags.is_once
-        if is_global_flag and one_turn:
-            _cprint("  ✗ /model --once cannot be combined with --global")
-            return
-        if one_turn and not model_input and not explicit_provider:
-            _cprint("  ✗ /model --once requires a model or provider.")
+        # via the shared single-owner parser (hermes_cli.model_switch).
+        request = parse_model_switch_args(raw_args)
+        model_input = request.target
+        explicit_provider = request.explicit_provider
+        is_global_flag = request.is_global
+        force_refresh = request.force_refresh
+        is_session = request.is_session
+        one_turn = request.is_once
+        if request.errors:
+            # CLI decoration: "  ✗ " prefix over the canonical error copy.
+            _cprint(f"  ✗ {request.error_messages()[0]}")
             return
         # Resolve the effective persistence once: --global forces persist,
         # --session/--once force session-scope, otherwise defer to