Show runnable task results in gutter

[pixel365]

Objective

• Make runnable task results visible directly in the editor gutter after running a test or task.
• This makes it easier to see whether the last run passed or failed without looking at the terminal output.

Solution

• Track the completion result for scheduled runnable tasks.
• Show the last runnable result in the gutter:
  • running task: accent play icon
  • successful task: success check icon
  • failed/cancelled task: error icon
• Apply the same status update path when running from the gutter play button and from inline code lens actions such as Run Test.

Testing

• Ran cargo check -p editor -p workspace.
• Ran cargo test -p workspace test_schedule_resolved_task_with_completion_reports_success.
• Manually tested running a GPUI test from the gutter play button.
• Manually tested running a GPUI test from the inline Run Test code lens.
• Verified the gutter icon updates after completion in both cases.

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]
  (https://github.com/zed-industries/zed/blob/main/crates/icons/README.md) guidelines)
• Tests cover the new/changed behavior
• Performance impact has been considered and is acceptable

Showcase

Before:

After:

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Release Notes:

• Improved runnable tasks by showing the last run result in the editor gutter.

[ChristopherBiscardi]

neat idea, and any file change seems to clear the status. It would be cool to have a followup where you can right-click to clear the status as well.

[pixel365]

Thanks! I opened #61375 for this.