Feature: Allow naming sessions for easier resume

Problem

When using claude --resume, sessions are listed by their first message preview, which makes it hard to identify which session to resume — especially when working on multiple projects or tasks in parallel.

Currently there's no way to name or tag a session, so you have to rely on memory or read session JSON files to figure out which is which.

Proposed Solution

Allow users to name a session, either at creation or during the session:

# Name at creation
claude --session-name "coverd-audience-analysis"

# Name during session (slash command)
/name coverd-audience-analysis

Then when resuming, show the name in the list:

claude --resume
? Select a session:
  [coverd-audience-analysis] Apr 28 — p11-new-advertiser-success
  [signal-eval-v8] Apr 24 — p2-signal-eval
  [unnamed] Apr 24 — ~/

And allow resuming by name:

claude --resume coverd-audience-analysis

Why This Matters

Power users often have multiple long-running sessions across different worktrees/projects. Being able to name and quickly find a session would significantly improve the workflow.

Alternatives Considered

• Using the first message as a description — works but is fragile and not always descriptive
• Manually inspecting ~/.claude/sessions/*.json — not user-friendly