Refine tab icon refresh scheduling

[ewgdg]

Summary

• Coalesce tab icon refreshes so only one refresh runs per animation frame.
• Gate refresh scheduling until layout is ready.
• Refresh icons when a tab header's icon element is silently replaced without triggering a layout-change event.

Repro

1. Install Iconic and obsidian-current-view (Current View) v1.4.0.
2. Switch between tabs multiple times to trigger view mode changes.
3. Observe the tab icon reset to default because Iconic does not reapply in that moment.

Testing

• Manually tested tab/view switches in Obsidian; icons remain stable.