Feature request: customizable sublists in background agent view

Feature request

Allow users to organize background agents into custom, named sublists in the agent/job view — and move agents between them.

Motivation

The current fixed categories (Running, Ready for Review, etc.) don't map well to real workflows. For example:

• An agent that created a PR and is now waiting for human review doesn't fit "Ready for Review" (that implies review of the agent's work by the user) or "Running" (it's idle). A user-defined "Awaiting PR Review" sublist would be perfect.
• Similarly, users might want sublists like "Blocked on CI", "Monitoring deploy", or "Paused — low priority".

Proposed behavior

1. Custom sublists: Users can create named sublists (e.g. "Awaiting PR Review", "Monitoring") in the agent view.
2. Move agents: Users can move an agent from one sublist to another — either manually or via an agent action (e.g. the agent itself could suggest which sublist it belongs in when it reaches a waiting state).
3. Dynamic naming: Sublists can be renamed or removed as workflows evolve.

This would turn the agent view from a status dashboard into a lightweight kanban for background work.

Related

See #58381 — sleeping/looping agents currently land in "Ready for Review" incorrectly, which partly stems from the fixed category model not having a good place for them.