Status line context usage doesn't update after /compact

Summary

After running /compact, the conversation context is successfully compacted, but the status line's context usage indicator does not update to reflect the reduced context. It continues showing the pre-compaction value until the next message is sent.

Steps to reproduce

1. Have a conversation that builds up significant context usage (e.g., 50%+)
2. Note the context usage shown in the status line
3. Run /compact
4. Observe that the status line still shows the old (higher) context usage percentage

The status line only updates after the next user message triggers a new API response.

Expected behavior

The status line should refresh its context usage display immediately after /compact completes, so the user gets visual confirmation that compaction worked.

Additional context

The status line currently updates on: new assistant messages, permission mode changes, and vim mode toggles. Since /compact doesn't trigger any of these, the display goes stale. A lightweight refresh after compaction would improve the UX without requiring an extra API call — the compaction response itself should carry updated context metrics.