Apply consistent sanitization to untrusted GitHub response fields

[SamMorrowDrums]

Describe the bug

Sanitization is applied by individual response converters, which leaves inconsistent coverage across issue comments, pull request bodies, reviews, review comments, releases, commit messages, and similar user-authored fields. Centralize or systematically audit response sanitization while preserving source-code and file-content fidelity.

Affected version

Current main as of 2026-08-19.

Steps to reproduce the behavior

1. Return user-authored text through different GitHub tools.
2. Compare fields processed by sanitize.Sanitize with fields returned directly.
3. Observe inconsistent filtering across equivalent untrusted-text surfaces.

Expected vs actual behavior

Expected: equivalent user-authored text is sanitized consistently, with a content-safe strategy for source code and file contents.

Actual: filtering depends on the converter used by each tool.

Logs

N/A