Desktop: stale 'PRs in review' entries cannot be dismissed

Description

The Claude Code Desktop home screen shows 16 stale "PRs in review" entries that cannot be dismissed. These appear to be orphaned worktree session records — no actual GitHub PRs exist (gh pr list returns empty), and no stale branches exist on the remote.

Steps to reproduce

1. Use Claude Code Desktop with worktree sessions over several conversations
2. Sessions appear as "PRs in review" on the home screen
3. There is no way to dismiss/close/archive these entries
4. Starting a new session still shows the same stale entries
5. Clicking an entry only offers "View PR" (which leads nowhere since no PR exists)

Expected behavior

• Entries should have a dismiss/close button
• Orphaned entries (where no GitHub PR actually exists) should auto-clear
• Starting a new session should not inherit stale review state

Environment

• Claude Code Desktop (macOS)
• All entries show "#1" and point to the same repo
• gh pr list --state open returns []
• git branch -a shows only main

Screenshot

16 entries showing "In review" status on the home screen with no way to dismiss them.