Fix editor presentation capture with pending styles

[chubes4]

Summary

• capture stable generated editor presentation identities without waiting for unrelated fonts or linked stylesheets
• cover an editor canvas whose linked stylesheet remains unavailable

Context

This blocked the solved-site promotion gate in Automattic/static-site-importer#1436: the editor was visible and valid and frontend screenshots were identical, but wordpress.editor-open omitted presentation evidence after timing out on unresolved style resources.

Verification

• npm run test:browser-routed-command-security
• npm run check (343 commands)
• git diff --check

AI Assistance

GPT-5.6 Sol via OpenCode analyzed the downstream promotion artifacts, implemented the focused runtime change and browser regression test, and ran the verification commands. I reviewed and orchestrated the work.