[FEATURE] Add delete functionality in /resume session selector

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

Currently, the /resume session selector provides useful features like:

• Preview sessions (P key)
• Rename sessions (R key)
• Search/filter sessions (/ key)

However, there's no way to delete old or unwanted sessions from the selector. Users must manually navigate to the filesystem to delete session files.

Proposed Solution

Add a delete shortcut key (e.g., D or Delete key) in the /resume session selector that allows users to:

1. Select a session in the selector
2. Press the delete key
3. Confirm deletion (optional safety prompt)
4. Remove the session permanently

Alternative Solutions

_No response_

Priority

Medium - Would be very helpful

Feature Category

CLI commands and flags

Use Case Example

As sessions accumulate over time, users need an easy way to clean up old or test sessions without leaving the CLI interface.

Additional Context

_No response_