Fix editor canvas probe authentication

[chubes4]

Summary

• install WordPress admin auth cookies before wordpress.editor-canvas-probe navigates to an editor target
• cover the authenticated portable front-page probe in the routed browser contract

Root cause

The probe resolved target=front-page to /wp-admin/post.php, but unlike the other editor commands it launched a fresh browser without installing WordPress auth cookies. Real runs redirected away from the editor and timed out with iframe-missing.

Verification

• npm run test:browser-routed-command-security
• npm run build
• SSI promotion evidence showed the preceding authenticated editor-open found one canvas iframe and 474/474 valid blocks; the unauthenticated probe alone failed

AI assistance

OpenAI GPT-5.6 Sol via OpenCode analyzed the retained CI browser artifacts, isolated the missing authentication call, implemented the focused fix, and ran the verification above. Chris Huber reviewed and orchestrated the work.