feat(system-ai): auto-load models on open + suitability hints (v0.13.1)

Two operator-felt papercuts on the editor:

  * Models only appeared after a manual Refresh click. Now the
    editor calls `_refreshModels()` from initState (post-frame)
    so chips populate immediately. Provider switch also re-fires
    the refresh because endpoint / model set changes too.

  * Operator had no signal which model is suitable. Tiny models
    fail at instruction following; huge models stall on a
    laptop. Adds a heuristic suitability rating (parses
    parameter count from common names like `gemma3:4b`,
    `llama3.2:70b`; falls back to family hints for OpenAI /
    Claude). Each chip now carries:
       - a coloured leading dot (green=balanced, orange=small
         or large, red=huge, grey=unknown)
       - a star icon for the hand-curated "tested with F∆I"
         allowlist (gemma3:4b, llama3.2:3b, qwen2.5-coder:7b,
         gpt-4o-mini, claude-haiku-4-5, …)
       - a tooltip ("balanced", "huge — likely too slow on a
         laptop", …)
    Sorting also moves recommended → balanced → others to the
    front so the operator's eye lands on green first.

  * Compact legend below the chip wrap explains the colour
    code in place — no lookup needed.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

lib/main.dart

@@ -23,7 +23,7 @@ import 'widgets/widgets.dart';
 /// Studio's own build version. Bump on every UI commit so the
 /// running app self-identifies — visible in the sidebar header
 /// and quick-glance proof that you're seeing the current build.
-const String kStudioVersion = '0.13.0';
+const String kStudioVersion = '0.13.1';
 
 Future<void> main() async {
   WidgetsFlutterBinding.ensureInitialized();