[FEATURE] Automatically set session name while making `plan`

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 frequently start working with plan mode, but claude code sets automatic session name only after start working on the plan.

In that workflow, there are no good timing to set session name until the end of plan making:

• System command /rename cannot sent while claude making/updating plan because queued message don't support system commands, and claude code won't stop
• In the plan's review dialog, also system command is not supported

Especially when the make plan -> review -> update plan -> review -> ... cycle, the session stay unnamed so long hours.

Proposed Solution

When claude code makes 1st draft of the plan document (or while working on plan making), set session name.

By making the plan, claude code should be able to know the topic.
And if it sets session name automatically, it is really helpful to distinguish many terminal tabs or mobile remote session list (especially mobile session is hard to find unless it named).

Alternative Solutions

Manually do /rename command before planning.

But, to do that, need to imagine and fix overview of the plan.
In many cases, claude code organizes my request well and points out key point of it, thus I want let claude names session based on claude's understanding

Priority

Medium - Would be very helpful

Feature Category

Other

Use Case Example

1. Enter plan mode
2. Write down many things that I want; at this moment the idea is not organized well
3. Claude code does good job to organize it, and set session name automatically based on it <- this is this issue's request
4. I could find terminal tab or mobile app session list easily by the name

Additional Context

_No response_