[FEATURE] Link and switch to named sessions from within a running session (TODO/task workflow)

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 maintain a persistent TODO list across Claude Code sessions using memory files. Each item maps to a session where the work was discussed. Today there's no way to reference a session from outside it, or switch to it without exiting the current session. I have to store the session name as plain text, exit, run claude -r "partial match", and hope the name hasn't changed.

Proposed Solution

1. A stable session reference (name or ID) that can be stored and used to locate a session later
2. /resume "session name" working from within a running session — park the current session, load the referenced one
3. Optionally, /resume back to return to the parked session

Related: #18401 (session linking/referencing) and #22978 (/new to switch without exiting). This combines both into a navigable workflow.

Alternative Solutions

Current workaround: store session name in a markdown file, exit, claude -r "search term". Works but breaks flow and relies on name matching. A /context-handoff skill can bridge the gap but loses the full conversation history.

Priority

Medium - Would be very helpful

Feature Category

CLI commands and flags

Use Case Example

My TODO list has: "Observations datasource filtering — blocked on UX decision. Session: observations include_missing and detailed_mode in dashboards". When the UX decision lands, I want to say "let's work on observations filtering" and have Claude switch to that session with full context, rather than starting fresh and re-reading all the code.

Additional Context

This would turn memory-based TODO lists into a navigable work queue. The building blocks exist (--resume, --name, /resume), the missing piece is in-session switching and a stable reference format.