feat: inline markdown annotations for plan review

[drankou]

Summary

Proof-of-concept for a better plan feedback UX (can be also extended on general .md files feedback) — instead of typing free-form chat messages, users can select text directly in a plan card, leave inline comments on specific passages, and send all collected comments back to the agent as a structured reply.

Inspired by agentation.dev.

How it works

1. Select text in a plan → floating popover appears for adding a comment
2. Annotated ranges get persistent highlights with numbered margin markers
3. "Reply with Comments" formats all annotations into a structured message and sends it to chat
4. Works in both inline plan cards and the fullscreen plan overlay

Demo:

md-annotations.mp4

[jjjrmy]

that's really cool!

[balintorosz]

Amazing! I've been willing to do this for a while! Will add it this week!