Session history disappears from sidebar after boot/cleanup — open sessions not shown in menu

After a system reboot, all sessions disappeared from the left sidebar menu, except for sessions that happened to be open as tabs. The sessions are intact on disk (.jsonl files) but are not restored to the menu.

Additionally, sessions currently open as tabs do not appear in the sidebar menu — they are completely separate lists with no overlap.

The .last-cleanup file timestamp matches exactly when the sessions disappeared from the menu (2026-05-19T12:35:05Z).

Expected: sidebar shows recent sessions from last N days, including currently open tab sessions.

Actual: sidebar only shows a small number of past sessions, cleared on boot, and open tabs are not listed.

Steps to reproduce:

1. Have multiple sessions open as tabs in VS Code extension
2. Reboot the system
3. Reopen VS Code with Claude Code extension
4. Observe: sidebar menu shows different sessions than the ones that were open as tabs

Version: 2.1.138
OS: Windows 10 Home 10.0.19045
Interface: VS Code extension