fix(browser): text tool, delete API headers, exhaustive Playwright tool tests

- Fix text tool: call updatePreview before confirmDraw so element is created
- Fix all DELETE requests: send Authorization only, no Content-Type body-less requests caused 400
- Add exhaustive Playwright test covering all 30 CAD tools on the actual canvas
- Verified: backend unit tests 254/254, frontend unit tests 380/380, browser tool tests 30/30

frontend/src/interaction/index.ts

@@ -593,6 +593,7 @@ export class InteractionEngine {
 
     // Text: single click placement, then prompt for text content
     if (this.state.activeTool === 'text') {
+      this.updatePreview(pt);
       this.confirmDraw();
       return;
     }