[FEATURE] Allow naming/labeling sessions so they're identifiable 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

Feature request

When using /resume, sessions are listed by timestamp only. There's no way to assign a human-readable label to a session, making it hard to find a specific conversation after a few days.

Current behavior

/resume shows sessions as a list ordered by recency, identified only by date/time. There is no way to search, filter, or label them.

Proposed Solution

Proposed behavior

Allow users to name the current session — either:

• A /name <label> command that tags the active session, or
• A prompt when starting a session ("Session name (optional):"), or
• Displaying the first user message as a preview in the /resume list (similar to how chat apps show conversation previpts)

The name/label would then appear in the /resume picker alongside the timestamp.

Alternative Solutions

_No response_

Priority

Medium - Would be very helpful

Feature Category

CLI commands and flags

Use Case Example

Use case

I run long review sessions (e.g. code reviews posted to multiple PRs) and want to be able to resume a specific one days later without scrolling through a list of unlabeled timestamps.

Additional Context

_No response_