Reject --with-comments without --json or document that it has no effect

[irl-dan]

Environment

• Margin 0.4.0
• macOS 26.2 (build 25C56)
• Apple silicon
• Package: Margin-0.4.0-macOS-arm64.pkg
• Package SHA-256: cb85c8f4bda5fa2c43fb775214d9ff5241d2143cf88d34088c3ea2dc975119a5

Summary

The read usage permits --with-comments without --json.
The command accepts this form.
The flag has no effect on human-readable output.
A user can believe that the output contains comments when it does not.

Reproduction steps

1. Create a Markdown file.
2. Add one comment.

margin comments add brief.md \
  --quote "The queue is the source of truth." \
  -m "What guarantees ordering during replay?" \
  --actor-type software \
  --actor-name clean-room-reviewer

3. Confirm that the comment exists.

margin comments validate brief.md --pretty

4. Read the command help.

margin read --help

5. Run the documented command form.

margin read brief.md --with-comments

Actual behavior

The command exits with status 0.
The output is identical to margin read brief.md.
The output does not contain the comment snapshot.
The usage line permits --with-comments without --json.
The option description states that the flag applies to JSON output.

Expected behavior

The CLI must prevent silent flag loss.
It should reject --with-comments unless --json is present.
As an alternative, the help and usage can require --json for this option.

Acceptance criteria

• margin read FILE --with-comments does not succeed silently.
• The error identifies the required --json option.
• The usage line shows the valid option combination.
• The same behavior applies to the show and cat aliases.
• Automated tests cover the invalid option combination.