[FEATURE] Sessions list (`claude agents` / `/agents`): custom groups instead of only Pinned / Needs input / Working / Completed

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

The sessions list (claude agents / /agents) groups rows only by status: Pinned / Needs input / Working / Completed. With ~25 sessions open (one per PR worktree, plus advisor/orchestrator sessions), status isn't how I think about the work: I want to see sessions by the spec / implementation plan they belong to, by PR stack, or by repo. Today the only workaround is a naming convention in the session name (🤖 PR 3 findings_read) and scanning, and the list isn't a hookable ui.render component, so a plugin can't regroup it either.

Proposed Solution

Let users define custom groups for the list, with the status groups kept as a secondary sort or prefix. Either:

• a --group <name> / -g flag on claude --bg and claude -n, a group field in claude agents --json, and the list grouped by it; or
• a settings key (e.g. agents.groupBy: "group" | "cwd" | "status") plus a way to set a session's group from inside it (a /rename-style command, or a $.session API for plugins).

Alternative Solutions

• Make the agents list a ui.render component so a mod can regroup it.
• Group by cwd parent directory, which already separates my worktrees from advisor sessions.

🤖 Generated with Claude Code