fix(web): wire browser-preview-context and extend RakazoDesktop interface

- Create browser-preview-context.ts (missing file causing Vite crash)
- Add browserPreview property to RakazoDesktop contract
- Fix executor-shell-guard.ts non-null assertion for body[cursor]

CLAUDE-RESUME-NOW.md

@@ -63,3 +63,10 @@
   - `conversationSidebarGroups` render simplified — only bots, removed dead `GroupAvatar` branch
   - `projectSidebarGroups` render uses `GroupAvatar` with proper members access
   - All TypeScript errors resolved (0 errors across apps/web and packages/adapters)
+- ✅ **browser-preview-context.ts** created (was missing from repo, caused Vite crash)
+  - Implements `browserPreviewActivity` subject with `.subscribe()`, `.set()`, `.snapshot()`, `.clear()`
+  - Multi-agent cursor tracking for browser preview panels
+- ✅ **RakazoDesktop interface** extended with optional `browserPreview` property
+  - Contract update in `packages/contracts/src/desktop.ts`
+  - Types: `navigate`, `reload`, `getState`, `onNavigate`, `onLoadingProgress`, `devServer`
+- ✅ **executor-shell-guard.ts** TS fix: `body[cursor]!` non-null assertion

apps/web/src/lib/browser-preview-context.ts

@@ -0,0 +1,46 @@
+/**
+ * Browser preview activity tracking.
+ *
+ * Shared state so Shell can display multi-agent cursor positions
+ * inside browser-preview panels.
+ */
+
+interface ActivityEntry {
+  x: number;
+  y: number;
+  label: string;
+}
+
+type Subscriber = (snapshot: ReadonlyMap<string, ActivityEntry>) => void;
+
+export const browserPreviewActivity = (() => {
+  const map = new Map<string, ActivityEntry>();
+  const listeners = new Set<Subscriber>();
+
+  const freeze = (): ReadonlyMap<string, ActivityEntry> =>
+    new Map(map) as ReadonlyMap<string, ActivityEntry>;
+
+  return {
+    subscribe(cb: Subscriber): () => void {
+      listeners.add(cb);
+      cb(freeze());
+      return () => {
+        listeners.delete(cb);
+      };
+    },
+
+    set(id: string, x: number, y: number, label: string): void {
+      map.set(id, { x, y, label });
+      listeners.forEach((l) => l(freeze()));
+    },
+
+    clear(id: string): void {
+      map.delete(id);
+      listeners.forEach((l) => l(freeze()));
+    },
+
+    snapshot(): ReadonlyMap<string, ActivityEntry> {
+      return freeze();
+    },
+  };
+})();

packages/adapters/src/executor-shell-guard.ts

@@ -441,7 +441,7 @@ function rubyScriptPaths(
     if (word.startsWith("--")) continue;
     const body = word.slice(1);
     for (let cursor = 0; cursor < body.length; cursor += 1) {
-      const letter = body[cursor];
+      const letter = body[cursor]!;
       const rest = body.slice(cursor + 1);
       if (letter === "e" || letter === "E") {
         inline = true;

packages/contracts/src/desktop.ts

@@ -66,6 +66,18 @@ export interface RakazoDesktop {
      */
     onCallback: (listener: (callback: RakazoDesktopOAuthCallback) => void) => () => void;
   };
+  /** Browser preview bridge — only available inside the Rakazo desktop app. */
+  browserPreview?: {
+    navigate: (url: string) => Promise<void>;
+    reload: () => Promise<void>;
+    getState: () => Promise<{ url: string; devServerRunning: boolean }>;
+    onNavigate: (listener: (url: string) => void) => () => void;
+    onLoadingProgress: (listener: (progress: number) => void) => () => void;
+    devServer: {
+      start: () => Promise<void>;
+      stop: () => Promise<void>;
+    };
+  };
 }
 
 /**