/resume missing sessions: sessions-index.json out of sync with actual session files

Bug

/resume doesn't show all past conversations. Sessions exist on disk as .jsonl files but are missing from sessions-index.json, making them invisible to the /resume picker.

Repro

1. Use Claude Code extensively over time (~160+ sessions)
2. Run /resume — only a subset of sessions appear
3. Compare actual .jsonl files on disk vs entries in sessions-index.json

Evidence

In my case:

• 162 .jsonl session files on disk in the project directory
• 98 entries in sessions-index.json
• 64 sessions (~40%) are orphaned — fully intact on disk but invisible to /resume

The missing sessions can still be resumed by passing the UUID directly (claude --resume <uuid>), confirming the data is fine — it's just the index that's stale.

Expected behavior

All sessions should appear in /resume. The index should stay in sync with session files on disk, or /resume should fall back to scanning the directory.

Environment

• macOS (Darwin 23.6.0)
• Claude Code v2.1.38