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

server/src/index.ts

@@ -668,6 +668,12 @@ export async function startServer(): Promise<StartedServer> {
     }, backupIntervalMs);
   }
   
+  // Wait for external adapters to finish loading before accepting requests.
+  // Without this, adapter type validation (assertKnownAdapterType) would
+  // reject valid external adapter types during the startup loading window.
+  const { waitForExternalAdapters } = await import("./adapters/registry.js");
+  await waitForExternalAdapters();
+
   await new Promise<void>((resolveListen, rejectListen) => {
     const onError = (err: Error) => {
       server.off("error", onError);