[FEATURE]: Session status management (Todo, Done, Backlog, etc.) for organizing AI sessions #21590

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Describe the enhancement you want to request

Problem

Currently, OpenCode sessions are a flat list with no way to organize or track their status. When working on multiple tasks across sessions, there's no way to mark sessions as "todo", "in progress", "done", "needs review", etc.

Existing issues like #18071 and #18564 address task-level todo lists within sessions, but this is about session-level status management — treating each AI session itself as a trackable work item.

Proposed Feature

Add session statuses and organization. For reference, Craft Agent implements this nicely in their desktop app (screenshot attached below):

• Statuses: Backlog, Todo, Needs Review, Done, Cancelled, Flagged, Archived
• Sidebar filtering: Sessions sorted/grouped by status for easy navigation
• Labels: User-defined tags for categorizing sessions (e.g., by project, priority)
• Agent self-management: Allow the agent to set its own session status (e.g., mark as "done" when finished)

Use Cases

1. Multi-task workflows — Keep track of which coding sessions need attention vs. are complete
2. Review workflow — Mark sessions as "Needs Review" for human follow-up
3. Automation triggers — Status changes could trigger webhooks or downstream actions
4. Session hygiene — Archive old sessions, flag important ones

Benefits

• Sessions become first-class trackable work items, not just chat threads
• Users can manage AI-assisted work like a lightweight task board
• Agents gain the ability to signal completion or request review
• Much better UX for power users managing many concurrent sessions

Screenshot

Craft Agent's session sidebar showing status-based organization: