[BUG] Plan-mode side-panel comments not delivered to assistant context

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

When using plan mode, the side panel allows inline annotations on the plan file (highlight a passage → leave a comment). The comments render in the UI but do not appear to be piped into the assistant's context on the next turn. Asking the assistant to "review the comments I left on the plan" returns nothing — the assistant only sees the underlying markdown body.

What Should Happen?

Comments should be actionable within UI. Currently the UI has no knowledge of the comments made in the panel.

Error Messages/Logs

Steps to Reproduce

Enter plan mode; let the assistant write a plan to ~/.claude/plans/<slug>.md
In the plan side panel, select a passage and add a comment (e.g., "sharpen this up")
Send a follow-up message asking the assistant to review the comments
Expected: Assistant receives the comment text along with the quoted passage it's attached to, and can respond against specific lines.

Claude Model

Opus

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.1.126

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Actual: Assistant has no visibility into side-panel comments. Only workaround is pasting comments back into chat as plain text, which defeats the UX advantage.

Environment: Claude Code 2.1.126, mobile/remote entrypoint, Opus 4.7.

Suggested fix: Inject submitted side-panel comments as a structured message (e.g., <plan-comments> block with quoted_text + comment pairs) on the next user turn, similar to how <github-webhook-activity> events are surfaced.