[FEATURE] Allow users to rename sessions shown in /resume

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

Claude Code's prompt cache warming gives returning to an old session
a meaningful performance advantage — context is already warm, making
the conversation faster and cheaper to continue. However, the current
/resume menu only shows auto-generated titles and timestamps, making
it difficult to locate the right session when managing multiple
parallel workflows.

This makes the cache warming benefit hard to exploit in practice,
because users can't reliably find the session they want to resume.

Proposed Solution

Add a /rename command (or equivalent) that lets users set a
human-readable name for the current session:

/rename "auto record"

The custom name would then appear in the /resume list in place of
(or alongside) the auto-generated title.

Alternatively, the /resume interface could support inline title
editing directly from the menu.

Alternative Solutions

_No response_

Priority

High - Significant impact on productivity

Feature Category

CLI commands and flags

Use Case Example

A user maintains several long-running, purpose-specific sessions
(e.g. one for video recording automation, one for a data pipeline,
one for a client project). Each session has accumulated relevant
context and warm cache. Without named sessions, the user must rely
on timestamps and auto-summaries to find the right one — which
becomes error-prone as the number of sessions grows.

Additional Context

_No response_