VSCode extension: Conversation timestamps reset to same time after restart

When using Claude Code in the VSCode sidebar (next to the Chat tab), restarting VSCode causes all conversation history timestamps to reset to the same time (presumably the restart time).

Steps to reproduce

1. Use Claude Code VSCode extension over multiple sessions, creating several conversations at different times
2. Restart VSCode (Cmd+Shift+P → "Reload Window" or quit/reopen)
3. Open the conversation history panel

Expected

Conversations retain their original "last edited" timestamps, with most recent conversations sorted to the top.

Actual

All conversations show the same timestamp (the restart time), making it impossible to identify and resume the most recent conversation.

Impact

With many conversations in history, finding the one you were just working on becomes a needle-in-a-haystack problem.

Environment

• macOS (Darwin 25.3.0)
• Claude Code VSCode extension (sidebar mode)
• Claude Opus 4.6