feat: P5 — first widget on screen (clock via SDK)

The dashboard finally has live content. `runtime.ts` now imports
`defineWidget` from `@dashward/widget-sdk` (added as a workspace
dependency of the container), defines a tabular-numerals clock widget
inline, and mounts it onto the 12-column grid via a generic
`mountWidget` + `createContext` pair that produces the SDK's
config/system/lifecycle/shell APIs.

container/runtime/runtime.ts
  - mountWidget(def, parent, instanceId, size): creates a grid card,
    applies grid-column/row span, builds the widget context, calls
    def.mount; wraps in try/catch so a mount failure visibly degrades
    the card (red border + error label) instead of breaking the page.
  - createContext: localStorage-backed config (persists per
    instanceId), theme reads dataset.theme and subscribes to the
    dashward:ThemeChanged CustomEvent (DBus signal forwarded from
    shell), shell.call delegates to window.__dashShell__. onMount
    fires via microtask; onUnmount handlers stored; visibility is a
    no-op until P7 (edit mode / workspace tracking).
  - clockDef: defineWidget<ClockConfig>; shadow DOM root, large
    tabular-numerals time string, re-renders on tick + config.onChange.

container/runtime/styles.css
  - Real card style: half-transparent backdrop-filter blur with a
    light/dark variant, rounded 18px corners, subtle border and shadow.
  - .widget-error fallback for failed mount.
  - grid-auto-rows: minmax(120px, auto) so widgets have a sensible
    minimum row height.

container/package.json
  - `@dashward/widget-sdk` is now a runtime dependency. esbuild
    bundles it into runtime.js.

Verified on ubuntu2504-test VM: clock card renders top-left at 4-wide
× 2-tall, ticks every second, follows system theme live via the P4
bridge (light → glass-white card, dark → glass-black card).

Layout persistence, edit mode, dynamic disk loading of widget bundles,
and iframe crash isolation per design §11 / §14 land in P6+.

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

container/runtime/runtime.ts

@@ -1,6 +1,16 @@
-// Page-side runtime (design §11). P4 establishes the shell-bridge and
-// uses it to follow the system color scheme. Real widget loading / edit
-// mode / layout persistence arrive in P5+.
+import { defineWidget } from '@dashward/widget-sdk';
+import type { Theme, WidgetContext, WidgetDefinition, WidgetHost } from '@dashward/widget-sdk';
+
+// =============================================================================
+// Page-side runtime (design §11). P5 mounts the first real widget on the
+// grid using the SDK's defineWidget abstraction. Layout persistence,
+// edit mode, and dynamic widget loading from disk arrive in later phases.
+// =============================================================================
+
+// -----------------------------------------------------------------------------
+// 1. Shell bridge — establishes window.__dashShell__ and follows the
+//    system color-scheme via the DBus round-trip (introduced in P4).
+// -----------------------------------------------------------------------------
 
 interface PendingCall {
   resolve(value: unknown): void;
@@ -58,14 +68,13 @@ const dashShell: DashShellInternal = {
 
 window.__dashShell__ = dashShell;
 
-// Theme: ask once on load, then follow ThemeChanged from the shell.
 function applyTheme(theme: unknown): void {
-  if (typeof theme !== 'string') return;
+  if (theme !== 'light' && theme !== 'dark') return;
   document.documentElement.dataset.theme = theme;
 }
 
 dashShell
-  .call<string>('getTheme')
+  .call<Theme>('getTheme')
   .then(applyTheme)
   .catch(e => console.warn('[dashward] getTheme failed:', e));
 
@@ -73,22 +82,155 @@ window.addEventListener('dashward:ThemeChanged', evt => {
   applyTheme((evt as CustomEvent<unknown>).detail);
 });
 
-// Remove the boot diagnostic now that runtime.js is executing.
-document.getElementById('boot')?.remove();
+// -----------------------------------------------------------------------------
+// 2. Widget mounting + context. P5 uses localStorage for config; shell-
+//    mediated persistence per design §9 lands when the widgets actually
+//    need cross-session config (clock's defaults are fine).
+// -----------------------------------------------------------------------------
 
-// Placeholder card so the dashboard workspace is visually distinct.
-const grid = document.getElementById('grid');
-if (grid) {
-  const placeholder = document.createElement('section');
-  placeholder.className = 'placeholder';
-  placeholder.innerHTML = `
-    <h1>Dashward</h1>
-    <p class="hint">P4 — shell bridge online.</p>
-    <p class="meta">Theme follows system. Widgets land in P5.</p>
-  `;
-  grid.appendChild(placeholder);
+function createContext<T>(def: WidgetDefinition<T>, instanceId: string): WidgetContext<T> {
+  const storageKey = `dashward:widget:${instanceId}:config`;
+
+  let stored: Partial<T> = {};
+  try {
+    const raw = localStorage.getItem(storageKey);
+    if (raw) stored = JSON.parse(raw) as Partial<T>;
+  } catch (e) {
+    console.warn(`[dashward] failed to read config for ${instanceId}:`, e);
+  }
+  let config: T = { ...def.defaultConfig, ...stored };
+
+  const configHandlers = new Set<(v: T) => void>();
+  const unmountHandlers = new Set<() => void>();
+
+  return {
+    config: {
+      get: () => config,
+      set: async (partial: Partial<T>) => {
+        config = { ...config, ...partial };
+        try {
+          localStorage.setItem(storageKey, JSON.stringify(config));
+        } catch (e) {
+          console.warn(`[dashward] failed to persist config for ${instanceId}:`, e);
+        }
+        for (const cb of configHandlers) cb(config);
+      },
+      onChange: (cb: (v: T) => void) => {
+        configHandlers.add(cb);
+        return () => configHandlers.delete(cb);
+      },
+    },
+    system: {
+      getTheme: () => (document.documentElement.dataset.theme as Theme) ?? 'light',
+      onThemeChange: (cb: (t: Theme) => void) => {
+        const h = (e: Event) => cb((e as CustomEvent<Theme>).detail);
+        window.addEventListener('dashward:ThemeChanged', h);
+        return () => window.removeEventListener('dashward:ThemeChanged', h);
+      },
+    },
+    lifecycle: {
+      onMount: (cb: () => void) => {
+        queueMicrotask(cb);
+      },
+      onUnmount: (cb: () => void) => {
+        unmountHandlers.add(cb);
+      },
+      // P5 doesn't track per-widget visibility; widgets stay alive as long
+      // as the dashboard page does. Returns a no-op unsubscriber.
+      onVisibilityChange: () => () => {},
+    },
+    shell: {
+      call: <R>(method: string, args?: unknown) => dashShell.call<R>(method, args),
+    },
+  };
 }
 
-console.info('[dashward-runtime] P4 bridge mounted');
+function mountWidget<T>(
+  def: WidgetDefinition<T>,
+  parent: HTMLElement,
+  instanceId: string,
+  size: { w: number; h: number },
+): void {
+  const element = document.createElement('div');
+  element.className = 'widget';
+  element.dataset.widget = def.id;
+  element.style.gridColumn = `span ${size.w}`;
+  element.style.gridRow = `span ${size.h}`;
+  parent.appendChild(element);
 
-export {};
+  const host: WidgetHost = { element, instanceId };
+  const ctx = createContext(def, instanceId);
+
+  try {
+    def.mount(host, ctx);
+  } catch (e) {
+    console.error(`[dashward] widget "${def.id}" mount failed:`, e);
+    element.classList.add('widget-error');
+    element.textContent = `${def.id}: mount failed`;
+  }
+}
+
+// -----------------------------------------------------------------------------
+// 3. Built-in clock widget (inline in runtime for now; a proper widget
+//    loader that reads widget.json from disk lands in P6+ along with the
+//    other builtins).
+// -----------------------------------------------------------------------------
+
+interface ClockConfig {
+  hour12: boolean;
+  showSeconds: boolean;
+}
+
+const clockDef = defineWidget<ClockConfig>({
+  id: 'clock',
+  defaultConfig: { hour12: false, showSeconds: true },
+
+  mount(host, ctx) {
+    const root = host.element.attachShadow({ mode: 'open' });
+    root.innerHTML = `
+      <style>
+        :host {
+          display: grid;
+          place-items: center;
+          width: 100%;
+          height: 100%;
+        }
+        .time {
+          font: 200 clamp(2rem, 7vw, 4.5rem) ui-sans-serif, system-ui, sans-serif;
+          font-variant-numeric: tabular-nums;
+          letter-spacing: -0.02em;
+        }
+      </style>
+      <div class="time"></div>
+    `;
+    const timeEl = root.querySelector('.time') as HTMLDivElement;
+
+    const render = (): void => {
+      const cfg = ctx.config.get();
+      timeEl.textContent = new Date().toLocaleTimeString(undefined, {
+        hour12: cfg.hour12,
+        hour: '2-digit',
+        minute: '2-digit',
+        second: cfg.showSeconds ? '2-digit' : undefined,
+      });
+    };
+
+    render();
+    const timer = setInterval(render, 1000);
+    ctx.lifecycle.onUnmount(() => clearInterval(timer));
+    ctx.config.onChange(() => render());
+  },
+});
+
+// -----------------------------------------------------------------------------
+// 4. Boot — remove the diagnostic banner, mount widgets.
+// -----------------------------------------------------------------------------
+
+document.getElementById('boot')?.remove();
+
+const grid = document.getElementById('grid');
+if (grid) {
+  mountWidget(clockDef, grid, 'clock-1', { w: 4, h: 2 });
+}
+
+console.info('[dashward-runtime] P5 mounted clock widget');

container/runtime/styles.css

@@ -2,6 +2,9 @@
   --bg: #f5f5f7;
   --fg: #1c1c1e;
   --fg-muted: rgba(28, 28, 30, 0.55);
+  --card: rgba(255, 255, 255, 0.7);
+  --card-border: rgba(0, 0, 0, 0.08);
+  --card-shadow: 0 8px 24px rgba(0, 0, 0, 0.06);
   --grid-gap: 16px;
 }
 
@@ -9,9 +12,13 @@
   --bg: #0f0f12;
   --fg: #f0f0f5;
   --fg-muted: rgba(240, 240, 245, 0.55);
+  --card: rgba(255, 255, 255, 0.06);
+  --card-border: rgba(255, 255, 255, 0.08);
+  --card-shadow: 0 8px 24px rgba(0, 0, 0, 0.4);
 }
 
-html, body {
+html,
+body {
   margin: 0;
   padding: 0;
   height: 100%;
@@ -24,15 +31,6 @@ body {
   -webkit-font-smoothing: antialiased;
 }
 
-#grid {
-  display: grid;
-  grid-template-columns: repeat(12, 1fr);
-  gap: var(--grid-gap);
-  padding: var(--grid-gap);
-  min-height: 100%;
-  box-sizing: border-box;
-}
-
 #boot {
   position: fixed;
   top: 16px;
@@ -46,31 +44,34 @@ body {
   z-index: 9999;
 }
 
-.placeholder {
-  grid-column: 1 / -1;
+#grid {
+  display: grid;
+  grid-template-columns: repeat(12, 1fr);
+  grid-auto-rows: minmax(120px, auto);
+  gap: var(--grid-gap);
+  padding: var(--grid-gap);
+  min-height: 100%;
+  box-sizing: border-box;
+}
+
+.widget {
+  background: var(--card);
+  border: 1px solid var(--card-border);
+  border-radius: 18px;
+  padding: 20px;
+  box-shadow: var(--card-shadow);
+  backdrop-filter: blur(12px);
+  -webkit-backdrop-filter: blur(12px);
+  overflow: hidden;
+  position: relative;
+  transition: transform 120ms ease, box-shadow 120ms ease;
+}
+
+.widget-error {
+  border-color: rgba(255, 80, 80, 0.6);
+  color: rgba(255, 80, 80, 0.95);
   display: grid;
   place-items: center;
-  align-content: center;
-  gap: 12px;
-  min-height: 80vh;
-  text-align: center;
-}
-
-.placeholder h1 {
-  font-size: clamp(3rem, 8vw, 6rem);
-  font-weight: 200;
-  letter-spacing: -0.02em;
-  margin: 0;
-}
-
-.placeholder .hint {
-  font-size: 1.25rem;
-  margin: 0;
-  opacity: 0.7;
-}
-
-.placeholder .meta {
-  font-size: 0.9rem;
-  margin: 0;
-  color: var(--fg-muted);
+  font-family: ui-monospace, monospace;
+  font-size: 12px;
 }