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

ui/src/adapters/metadata.ts

@@ -0,0 +1,61 @@
+/**
+ * Adapter metadata utilities — built on top of the display registry and UI adapter list.
+ *
+ * This module bridges the static display metadata with the dynamic adapter registry.
+ * "Coming soon" status is derived from the display registry's `comingSoon` flag.
+ * "Hidden" status comes from the disabled-adapter store (server-side toggle).
+ */
+import type { UIAdapterModule } from "./types";
+import { listUIAdapters } from "./registry";
+import { isAdapterTypeHidden } from "./disabled-store";
+import { getAdapterLabel, getAdapterDisplay } from "./adapter-display-registry";
+
+export interface AdapterOptionMetadata {
+  value: string;
+  label: string;
+  comingSoon: boolean;
+  hidden: boolean;
+}
+
+export function listKnownAdapterTypes(): string[] {
+  return listUIAdapters().map((adapter) => adapter.type);
+}
+
+/**
+ * Check whether an adapter type is enabled (not "coming soon").
+ * Unknown types (external adapters) are always considered enabled.
+ */
+export function isEnabledAdapterType(type: string): boolean {
+  return !getAdapterDisplay(type).comingSoon;
+}
+
+/**
+ * Build option metadata for a list of adapters (for dropdowns).
+ * `labelFor` callback allows callers to override labels; defaults to display registry.
+ */
+export function listAdapterOptions(
+  labelFor?: (type: string) => string,
+  adapters: UIAdapterModule[] = listUIAdapters(),
+): AdapterOptionMetadata[] {
+  const getLabel = labelFor ?? getAdapterLabel;
+  return adapters.map((adapter) => ({
+    value: adapter.type,
+    label: getLabel(adapter.type),
+    comingSoon: !!getAdapterDisplay(adapter.type).comingSoon,
+    hidden: isAdapterTypeHidden(adapter.type),
+  }));
+}
+
+/**
+ * List UI adapters excluding those hidden via the Adapters settings page.
+ */
+export function listVisibleUIAdapters(): UIAdapterModule[] {
+  return listUIAdapters().filter((a) => !isAdapterTypeHidden(a.type));
+}
+
+/**
+ * List visible adapter types (for non-React contexts like module-level constants).
+ */
+export function listVisibleAdapterTypes(): string[] {
+  return listVisibleUIAdapters().map((a) => a.type);
+}