feat: add clipboard API for remote browser clipboard access

POST /api/clipboard with { text } broadcasts to all connected browsers
via SSE. Browser attempts navigator.clipboard.writeText, falling back
to a modal with manual copy button if blocked.

Enables remote clipboard workflows: CLI tools can push text to the
user's browser clipboard across the network.

src/web/routes/clipboard-routes.ts

@@ -0,0 +1,24 @@
+/**
+ * @fileoverview Clipboard routes.
+ * Accepts text via POST and broadcasts to connected browsers for clipboard write.
+ */
+
+import { FastifyInstance } from 'fastify';
+import { SseEvent } from '../sse-events.js';
+import type { EventPort } from '../ports/index.js';
+
+export function registerClipboardRoutes(app: FastifyInstance, ctx: EventPort): void {
+  app.post('/api/clipboard', async (req) => {
+    const body = req.body as { text?: string; sessionId?: string };
+    const text = body?.text;
+    if (typeof text !== 'string' || text.length === 0) {
+      return { success: false, error: 'Missing or empty "text" field' };
+    }
+    ctx.broadcast(SseEvent.ClipboardWrite, {
+      text,
+      sessionId: body.sessionId ?? null,
+      timestamp: Date.now(),
+    });
+    return { success: true };
+  });
+}

src/web/routes/index.ts

@@ -15,4 +15,5 @@ export { registerRespawnRoutes } from './respawn-routes.js';
 export { registerRalphRoutes } from './ralph-routes.js';
 export { registerPlanRoutes } from './plan-routes.js';
 export { registerOrchestratorRoutes } from './orchestrator-routes.js';
+export { registerClipboardRoutes } from './clipboard-routes.js';
 export { registerWsRoutes } from './ws-routes.js';