feat(text-tool): implement Photoshop-style on-canvas text editor

- Replaced modal dialog with inline on-canvas text editor
- Text objects stored as editable entities (non-rasterized)
- Live preview with transparent textarea overlay
- Click on existing text to re-edit
- Drag transform handles to move text
- Auto-commit on click outside (via overlay)
- Text selection with visible highlight
- Hidden original text during editing to prevent double vision
- Position alignment fixes for editing existing text
- Keyboard shortcuts: Ctrl+Enter to commit, Escape to cancel

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

tools/text-tool.ts

@@ -18,9 +18,18 @@ export class TextTool extends BaseTool {
     const layer = this.getActiveLayer();
     if (!layer) return;
 
-    // Open text dialog at click position
-    const { openDialog } = useTextStore.getState();
-    openDialog(pointer.x, pointer.y);
+    const { activateOnCanvasEditor, getTextObjectAt } = useTextStore.getState();
+
+    // Check if clicking on existing text object
+    const existingText = getTextObjectAt(pointer.x, pointer.y, layer.id);
+
+    if (existingText) {
+      // Edit existing text
+      activateOnCanvasEditor(pointer.x, pointer.y, existingText.id);
+    } else {
+      // Create new text
+      activateOnCanvasEditor(pointer.x, pointer.y);
+    }
   }
 
   onPointerMove(): void {