fix(copilot): use gpt-4.1 as default model and 127.0.0.1 for local connections

Key changes:
- Changed default model from claude-sonnet-4.5 to gpt-4.1 (free tier compatible)
- Updated all Claude models to minPlan: 'pro' (requires paid Copilot subscription)
- Replaced 'localhost' with '127.0.0.1' for more reliable local connections
  (bypasses DNS resolution and potential IPv6 issues)
- Updated UI presets: replaced Claude Haiku with Raptor Mini in free tier
- Fixed FREE_PRESETS to only include actually free models

This fixes the "model_not_supported" error when using free tier GitHub Copilot
subscription, which doesn't have access to Claude models.

src/copilot/copilot-executor.ts

@@ -40,8 +40,10 @@ export function generateCopilotEnv(config: CopilotConfig): Record<string, string
   const sonnetModel = config.sonnet_model || config.model;
   const haikuModel = config.haiku_model || config.model;
 
+  // Use 127.0.0.1 instead of localhost for more reliable local connections
+  // (bypasses DNS resolution and potential IPv6 issues)
   return {
-    ANTHROPIC_BASE_URL: `http://localhost:${config.port}`,
+    ANTHROPIC_BASE_URL: `http://127.0.0.1:${config.port}`,
     ANTHROPIC_AUTH_TOKEN: 'dummy', // copilot-api handles auth internally
     ANTHROPIC_MODEL: config.model,
     // Model tier mapping - allows different models for opus/sonnet/haiku