[BUG] Cowork project sidebar shows unexplained caution badge; stale session error persists indefinitely with no way to diagnose or clear it in the UI

Summary

A Cowork project's sidebar icon showed a persistent orange warning triangle with no tooltip, no detail view, and no explanation anywhere in the UI. It survived app restarts.

Root cause (traced through ion-dist sidebar code)

The project row aggregates session states and renders an error badge if any session record has a persisted error field. One session's local JSON (under ~/Library/Application Support/Claude/local-agent-mode-sessions/.../local_<id>.json) contained error: "Claude Code process exited with code 1" from a crashed run weeks earlier. The error never cleared on subsequent launches. Removing the field from the session file and restarting cleared the badge.

Issues

1. The badge element is aria-hidden with no affordance, so users cannot discover what it means (no tooltip, nothing in the project menu or settings).
2. A terminal session error persists indefinitely instead of clearing or expiring.
3. Nothing indicates which session caused a project-level badge (90 sessions in this project; one crashed background run was the trigger).

Suggested fixes

• Tooltip or detail view on the badge naming the failing session.
• Clear or age out stale process-exit errors on app launch.

Environment

macOS, latest Claude Desktop (August 2026).