fix: use cache file for model availability instead of SDK calls

- Changed fetchAvailableModels to read from ~/.cache/opencode/models.json
- Prevents plugin startup hanging caused by SDK client.config.providers() call
- Updated doctor model-resolution check to show available models from cache
- Added cache info display: provider count, model count, refresh command

src/index.ts

@@ -79,6 +79,7 @@ import { createModelCacheState, getModelLimit } from "./plugin-state";
 import { createConfigHandler } from "./plugin-handlers";
 
 const OhMyOpenCodePlugin: Plugin = async (ctx) => {
+  log("[OhMyOpenCodePlugin] ENTRY - plugin loading", { directory: ctx.directory })
   // Start background tmux check immediately
   startTmuxCheck();