feat(adapters): external adapter plugin system with dynamic UI parser

- Plugin loader: install/reload/remove/reinstall external adapters
  from npm packages or local directories
- Plugin store persisted at ~/.paperclip/adapter-plugins.json
- Self-healing UI parser resolution with version caching
- UI: Adapter Manager page, dynamic loader, display registry
  with humanized names for unknown adapter types
- Dev watch: exclude adapter-plugins dir from tsx watcher
  to prevent mid-request server restarts during reinstall
- All consumer fallbacks use getAdapterLabel() for consistent display
- AdapterTypeDropdown uses controlled open state for proper close behavior
- Remove hermes-local from built-in UI (externalized to plugin)
- Add docs for external adapters and UI parser contract

packages/adapter-utils/src/types.ts

@@ -292,7 +292,7 @@ export interface ServerAdapterModule {
    * Returns the detected model/provider and the config source, or null if
    * the adapter does not support detection or no config is found.
    */
-  detectModel?: () => Promise<{ model: string; provider: string; source: string } | null>;
+  detectModel?: () => Promise<{ model: string; provider: string; source: string; candidates?: string[] } | null>;
 }
 
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