[BUG] Stale 'update available' message shown after resuming a session post-upgrade

Description

After upgrading Claude Code via brew upgrade claude-code and resuming a previous session, the yellow 'Update available! Run: brew upgrade claude-code' message is still shown in the status bar, even though the upgrade has already been applied.

Steps to reproduce

1. Have a Claude Code update available — the status bar shows the 'Update available!' message - exit claude code
2. Run brew upgrade claude-code to apply the upgrade
3. Resume the previous Claude Code session (rather than starting a new one)
4. The stale 'Update available!' message is still visible in the status bar

Expected behaviour

The status bar message should either be cleared on resume, or the version check should be re-run when a session is resumed.

Actual behaviour

The stale update message from the previous session is reinstated as-is, even though the upgrade has already been applied.

Environment

• Platform: macOS
• Install method: Homebrew