bug[cli] :: gh comment body may post literal \n sequences

Summary

When Codex posts GitHub issue comments via shell/gh, escaped newline sequences can be sent literally (e.g., \\n) instead of rendered as actual line breaks.

Expected

• Multiline comment text renders with real new lines.

Actual

• Comment contains literal \\n text.

Repro (high level)

1. Use Codex to post an issue comment via shell command with escaped newlines in a quoted body.
2. Observe rendered comment contains backslash-n sequences.

Evidence

• Downstream tracking issue documenting the behavior: https://github.com/bniladridas/browser/issues/362
• Affected comments:
• https://github.com/bniladridas/browser/issues/358#issuecomment-4010468673
• https://github.com/bniladridas/browser/issues/358#issuecomment-4010469458
• https://github.com/bniladridas/browser/issues/358#issuecomment-4010472889
• Correctly formatted follow-up (HEREDOC body):
• https://github.com/bniladridas/browser/issues/358#issuecomment-4010474953

Suggested fix

• In Codex command generation, avoid escaped newline literals for GH comment bodies; prefer HEREDOC-style body composition or explicit multiline payload handling.