Render page titles as untrusted Markdown content

[Driedsandwich]

Summary

• Move the page title out of trusted-looking source metadata.
• Label it as untrusted page content and render it in a dynamically sized Markdown fence.
• Keep body and comment handling, permissions, and local-only behavior unchanged.

Related Issue and acceptance criteria

• Issue: Addresses [Privacy] Treat page titles as untrusted Markdown content #6
• Acceptance criteria: adversarial title text cannot create exported headings, image syntax, or an early closing fence; the title remains clearly labeled as untrusted.

Changes

• Add a Markdown-inert untrusted title section.
• Update public documentation to describe the title boundary.
• Add an adversarial title regression with embedded Markdown and backticks.

Verification

• npm test — 38/38 passed
• Manual verification completed against exact head 44a5f4c74f08b2441264cb5d9cd304badc40fa45
• Repository sanity workflow reproduced locally
• Gitleaks 8.30.1 exact tree and introduced range — finding 0
• Codex Security exact diff scan 4321da9a-7043-444c-993b-bc4b520f9d8b — finding 0
• Isolated headed Chrome for Testing 152: public-safe Issue, Pull Request Conversation, unsupported page, Copy, Download, and permission checks passed

Risk review

• Permission impact: none; remains activeTab, scripting, clipboardWrite, with no host permissions
• Privacy impact: improves the trust boundary around attacker-influenced page titles
• Dependency impact: none
• Network or external-communication impact: none; no API or external transmission added

Scope check

• No unrelated refactor or formatting changes
• No credentials, private content, personal data, or private screenshots
• Documentation updated or an explicit reason given
• No new completeness, production-readiness, or security-scanner claim

[chatgpt-codex-connector]

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Reviewed commit: 44a5f4c74f

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[chatgpt-codex-connector]

Align manual checks with the relocated title

When a maintainer follows the repository's verification procedure, this new section makes the documented checks fail: docs/07_manual_verification.md lines 51, 79, and 123 still require the title under Source, and docs/08_manual_verification_result_template.md lines 48 and 69 repeat that requirement, even though Source now contains only the URL. Update both checklists to verify the fenced Untrusted Page Title section so future manual results reflect the implemented output.

AGENTS.md reference: AGENTS.md:L58-L58

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