Text tool: start empty with cursor, blue editing outline

- Create text nodes with empty text instead of 'Text' placeholder
- Immediately enter editing mode on creation (blinking cursor)
- Blue border on textarea during editing (matches Figma)

src/components/EditorCanvas.vue

@@ -69,7 +69,7 @@ function onTextKeyDown(e: KeyboardEvent) {
     <canvas ref="canvasRef" :style="{ cursor }" class="block size-full" />
     <textarea
       v-if="editingNode"
-      class="absolute z-10 resize-none overflow-hidden border-none bg-transparent p-0 font-normal text-black outline-none"
+      class="absolute z-10 resize-none overflow-hidden border border-accent bg-transparent p-0 font-normal text-black outline-none"
       :style="textOverlayStyle!"
       :value="editingNode.text"
       @input="onTextInput"

src/composables/use-canvas-input.ts

@@ -387,8 +387,9 @@ export function useCanvasInput(canvasRef: Ref<HTMLCanvasElement | null>, store:
     // Text tool: click to create text node
     if (tool === 'TEXT') {
       const nodeId = store.createShape('TEXT', cx, cy, 200, 24)
-      store.graph.updateNode(nodeId, { text: 'Text' })
+      store.graph.updateNode(nodeId, { text: '' })
       store.select([nodeId])
+      store.startTextEditing(nodeId)
       store.setTool('SELECT')
       store.requestRender()
       return