fix(browser): expect external editor presentation identities

[chubes4]

Summary

• collect canonical 64-hex versions from stylesheets enqueued for editor content
• preserve inline presentation marker collection
• normalize, deduplicate, and sort the combined expected identity set
• cover inline-only, external-only, mixed, malformed, and unrelated stylesheet delivery

Verification

• npx tsx --test tests/editor-presentation-contract.test.ts
• npm run build
• npm run test:browser-routed-command-security

Fixes #2452.

AI assistance

OpenAI GPT-5.6 Sol via OpenCode analyzed the downstream promotion evidence, implemented and reviewed the bounded contract change, and ran the verification gates. Chris Huber directed and owns the work.