chore: P0 skeleton

Bootstrap the Dashward repo per arch/UBUNTU-DASHBOARD-SPACE.md:

- pnpm-workspaces monorepo (sdk, extension, container, widgets-builtin/*)
- GNOME extension stub (metadata.json, src/*.ts placeholders for warden,
  guard, supervisor, entry UX, DBus service)
- WebKit container stub (GJS main + page-side runtime + dashboard.html)
- TypeScript widget SDK (defineWidget + types)
- Builtin clock widget as the first SDK consumer example
- DBus interface XML (proto/shell.iface.xml) and shared types
- esbuild configs for extension and container; tsc for SDK
- Design doc copied in at repo root for discoverability

No functional logic yet -- all components are placeholders that compose
in extension.ts so the build chain can be exercised. P1 (workspace
warden) starts next.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

extension/widgets-builtin/clock/src/index.ts

@@ -0,0 +1,41 @@
+import { defineWidget } from '@dashward/widget-sdk';
+
+interface ClockConfig {
+  hour12: boolean;
+  showSeconds: boolean;
+}
+
+export default defineWidget<ClockConfig>({
+  id: 'clock',
+  defaultConfig: { hour12: false, showSeconds: true },
+
+  mount(host, { config, lifecycle, system }) {
+    const root = host.element.attachShadow({ mode: 'open' });
+    root.innerHTML = `
+      <style>
+        :host { display: grid; place-items: center; }
+        .time { font: 600 clamp(2rem, 8vw, 5rem) ui-sans-serif, system-ui; }
+        :host([data-theme="dark"]) .time { color: #f0f0f0; }
+      </style>
+      <div class="time"></div>
+    `;
+    const el = root.querySelector('.time') as HTMLDivElement;
+
+    const render = () => {
+      const cfg = config.get();
+      el.textContent = new Date().toLocaleTimeString(undefined, {
+        hour12: cfg.hour12,
+        hour: '2-digit',
+        minute: '2-digit',
+        second: cfg.showSeconds ? '2-digit' : undefined,
+      });
+    };
+
+    const timer = setInterval(render, 1000);
+    render();
+    lifecycle.onUnmount(() => clearInterval(timer));
+
+    config.onChange(render);
+    system.onThemeChange(t => (host.element.dataset.theme = t));
+  },
+});