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/__tests__/agent-skills-routes.test.ts

@@ -86,6 +86,7 @@ vi.mock("../services/index.js", () => ({
 vi.mock("../adapters/index.js", () => ({
   findServerAdapter: vi.fn(() => mockAdapter),
   listAdapterModels: vi.fn(),
+  detectAdapterModel: vi.fn(),
 }));
 
 function createDb(requireBoardApprovalForNewAgents = false) {