Emit agent thread status change events

[dscarpetti]

Objective

Fix unreliable working/status indicators for ACP agent threads.

ACP threads update their internal running state when a turn starts, completes, or is canceled, but those status-only changes were not being emitted as thread events. The agent UI could miss transitions unless another entry-related event happened nearby, making it particularly hard to monitor the status of multiple agent threads running at once.

Hope this helps, and thanks for making Zed.

Solution

• Add an AcpThreadEvent::StatusChanged event.
• Emit it when running_turn is set, cleared, or canceled.
• Have ConversationView handle the event by syncing the active thread view's generating indicator.
• Treat status changes as UI state only, not root thread metadata changes.

Testing

• cargo check -p sidebar -p project -p git_ui -p workspace
• Manually verified in a local dev build on macOS that ACP agent status/working indicators update reliably.

No automated test was added; this changes UI synchronization for ACP thread status events.

Self-Review Checklist:

• I've reviewed my own diff for quality, security, and reliability
• Unsafe blocks (if any) have justifying comments
• The content adheres to Zed's UI standards (UX/UI and icon guidelines)
• Tests cover the new/changed behavior
• Performance impact has been considered and is acceptable

---

Release Notes:

• Fixed unreliable working indicators for ACP agent threads.

[cla-bot]

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[NguyenCuong1989]

pl

[benbrandt]

thanks!