[FEATURE] [DESKTOP] Plan UI inline comments, similar to code diff inline comments

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

I looked around and didn't find anything asking for exactly this, so figured I would make a separate issue for this request. This request is specific to Claude Code on the desktop app.

Today, when reviewing a plan, the only real way you give feedback is by hitting ESC, provide some text to the "Revise" popup. This is _fine_, but it can be imprecise, especially on larger plans where you want to make some more targeted edits or ask questions about specific aspects of the plan that came up. I've basically resorted to essentially re-stating what was said in the plan so that I can give Claude more guidance.

Proposed Solution

I would like to select one or more lines / paragraphs and comment on them inline, just like how you can do that in the code diffs, e.g. this:

<img width="1470" height="598" alt="Image" src="https://github.com/user-attachments/assets/a6f64bc7-b932-49f3-8027-236b6a8018af" />

Being able to do this on a plan to make targeted revisions / ask questions would be a really nice addition to the desktop UI

Alternative Solutions

The only real solution right now (I think?) is to do what I said above - reject with guidance, but the guidance has to be descriptive about what portion of the plan you want to change. It works well enough, but it could be better.

Priority

Medium - Would be very helpful

Feature Category

Other

Use Case Example

You're working with Claude to come up with a plan, and you're reviewing it with them. That's the exact use case, I don't think I can be any more straightforward than that.

Additional Context

_No response_