feat(code): add Esc to exit code mode, project indicator pill, design token context

- Escape key exits code mode on desktop (T14)
- Show active project name pill near chat input when in code mode (T15)
- Inject selected design tokens, files, and open file content into AI
  system prompt when in code mode (T16)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/app/src/components/chat/ChatWindow.vue

@@ -103,6 +103,24 @@
       class="flex-1 min-h-0"
     />
 
+    <!-- Code mode project indicator -->
+    <div
+      v-if="codeContext.isCodeMode.value && codeContext.activeProject.value"
+      class="px-3 pb-1 flex items-center gap-1.5"
+    >
+      <span class="text-[10px] px-2 py-0.5 rounded-md bg-accent/15 text-accent font-medium truncate max-w-[200px]">
+        {{ codeContext.activeProject.value.name }}
+      </span>
+      <button
+        class="text-white/30 hover:text-white/60 transition-colors p-0.5"
+        @click="codeContext.exitCodeMode()"
+      >
+        <svg class="w-3 h-3" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+          <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M6 18L18 6M6 6l12 12" />
+        </svg>
+      </button>
+    </div>
+
     <ChatInput
       :disabled="isStreaming || comparison.isAnyStreaming.value"
       :streaming="isStreaming || comparison.isAnyStreaming.value"