[feat]: add cross-agent task comparison board

[Drakaniia]

Feature Summary

Add a project-level comparison board that lets users evaluate multiple agent-created tasks side by side. The board should show task status, agent/provider, branch, diff stats, changed files, PR/check status, and quick actions to open, accept, archive, or delete a result.

Problem or Use Case

Emdash is built around running multiple coding agents in parallel, but users currently have to inspect each task one at a time. That makes it hard to compare competing solutions, identify the best result, spot stale or incomplete work, and clean up rejected attempts.

This weakens the core “parallel agents” workflow because the final decision still happens manually across separate task views.

Proposed Solution

Add a new project-level Compare view alongside Tasks, Pull Requests, and Settings.

The comparison board should include:

• A list or table of active and recently completed tasks for the project.
• Agent/provider, task name, branch name, task status, and last activity.
• Diff stats such as files changed, additions, deletions, staged/unstaged state.
• PR state when available, including draft/open/merged status and checks.
• Quick actions:
  • Open task
  • Open diff
  • Create or open PR
  • Pin/mark as preferred
  • Archive rejected task
  • Delete failed/unused task after confirmation

The first implementation can focus on local project/task metadata already available in the renderer stores, then expand to richer PR and test-result signals later.

Alternatives Considered

Users can currently open each task manually from the task list and compare diffs one at a time. This works for small cases but does not scale when several agents are running in parallel on the same problem.

Another option is improving the existing task list with more metadata, but that would overload the task management surface. A dedicated comparison view better matches the review-and-selection workflow.

Additional Context

Evidence from the current product surface:

• Project navigation currently has Tasks, Pull Requests, and Settings.
• Task review capabilities already exist in individual task views: diffs, PR state, checks, conversations, and terminals.
• The missing layer is a project-level aggregation surface for comparing parallel outputs.

[arnestrickmann]

@Drakaniia, thank you for raising this. This makes a lot of sense for Emdash’s parallel-agent workflow, and we’ll keep it in mind as we shape upcoming project-level review and comparison surfaces.