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/dynamic-loader.ts

@@ -0,0 +1,106 @@
+/**
+ * Dynamic UI parser loading for external adapters.
+ *
+ * When the Paperclip UI encounters an adapter type that doesn't have a
+ * built-in parser (e.g., an external adapter loaded via the plugin system),
+ * it fetches the parser JS from `/api/adapters/:type/ui-parser.js` and
+ * evaluates it to create a `parseStdoutLine` function.
+ *
+ * The parser module must export:
+ *   - `parseStdoutLine(line: string, ts: string): TranscriptEntry[]`
+ *   - optionally `createStdoutParser(): { parseLine, reset }` for stateful parsers
+ *
+ * This is the bridge between the server-side plugin system and the client-side
+ * UI rendering. Adapter developers ship a `dist/ui-parser.js` with zero
+ * runtime dependencies, and Paperclip's UI loads it on demand.
+ */
+
+import type { TranscriptEntry } from "@paperclipai/adapter-utils";
+import type { StdoutLineParser } from "./types";
+
+// Cache of dynamically loaded parsers by adapter type.
+// Once loaded, the parser is reused for all runs of that adapter type.
+const dynamicParserCache = new Map<string, StdoutLineParser>();
+
+// Track which types we've already attempted to load (to avoid repeat 404s).
+const failedLoads = new Set<string>();
+
+/**
+ * Dynamically load a UI parser for an adapter type from the server API.
+ *
+ * Fetches `/api/adapters/:type/ui-parser.js`, evaluates the module source
+ * in a scoped context, and extracts the `parseStdoutLine` export.
+ *
+ * @returns A StdoutLineParser function, or null if unavailable.
+ */
+export async function loadDynamicParser(adapterType: string): Promise<StdoutLineParser | null> {
+  // Return cached parser if already loaded
+  const cached = dynamicParserCache.get(adapterType);
+  if (cached) return cached;
+
+  // Don't retry types that previously 404'd
+  if (failedLoads.has(adapterType)) return null;
+
+  try {
+    const response = await fetch(`/api/adapters/${encodeURIComponent(adapterType)}/ui-parser.js`);
+    if (!response.ok) {
+      failedLoads.add(adapterType);
+      return null;
+    }
+
+    const source = await response.text();
+
+    // Evaluate the module source using URL.createObjectURL + dynamic import().
+    // This properly supports ESM modules with `export` statements.
+    // (new Function("exports", source) would fail with SyntaxError on `export` keywords.)
+    const blob = new Blob([source], { type: "application/javascript" });
+    const blobUrl = URL.createObjectURL(blob);
+
+    let parseFn: StdoutLineParser;
+
+    try {
+      const mod = await import(/* @vite-ignore */ blobUrl);
+
+      // Prefer the factory function (stateful parser) if available,
+      // fall back to the static parseStdoutLine function.
+      if (typeof mod.createStdoutParser === "function") {
+        // Stateful parser — create one instance for the UI session.
+        // Each run creates its own transcript builder, so a single
+        // parser instance is sufficient per adapter type.
+        const parser = (mod.createStdoutParser as () => { parseLine: StdoutLineParser; reset: () => void })();
+        parseFn = parser.parseLine.bind(parser);
+      } else if (typeof mod.parseStdoutLine === "function") {
+        parseFn = mod.parseStdoutLine as StdoutLineParser;
+      } else {
+        console.warn(`[adapter-ui-loader] Module for "${adapterType}" exports neither parseStdoutLine nor createStdoutParser`);
+        failedLoads.add(adapterType);
+        return null;
+      }
+    } finally {
+      URL.revokeObjectURL(blobUrl);
+    }
+
+    // Cache for reuse
+    dynamicParserCache.set(adapterType, parseFn);
+    console.info(`[adapter-ui-loader] Loaded dynamic UI parser for "${adapterType}"`);
+    return parseFn;
+  } catch (err) {
+    console.warn(`[adapter-ui-loader] Failed to load UI parser for "${adapterType}":`, err);
+    failedLoads.add(adapterType);
+    return null;
+  }
+}
+
+/**
+ * Invalidate a cached dynamic parser, removing it from both the parser cache
+ * and the failed-loads set so that the next load attempt will try again.
+ */
+export function invalidateDynamicParser(adapterType: string): boolean {
+  const wasCached = dynamicParserCache.has(adapterType);
+  dynamicParserCache.delete(adapterType);
+  failedLoads.delete(adapterType);
+  if (wasCached) {
+    console.info(`[adapter-ui-loader] Invalidated dynamic UI parser for "${adapterType}"`);
+  }
+  return wasCached;
+}