[mahkoh]

Fixes #1308

[Copilot]

🟢 Approval recommended

No blocking issues were identified in visibility handling, transaction damage scheduling, or rectangle-union behavior.

No open issues 🎉

What changed in this PR

This PR reduces unnecessary status-bar rendering and output damage to address the frame drops reported in #1308.

Changes:

• Tracks bar visibility in live and render state, skipping status-triggered rendering while hidden.
• Avoids full-output damage for render-data-only transactions.
• Makes rectangle unions handle empty rectangles directly, simplifying callers.

File	Description
src/​tree/​output/​output_dfs_g_fuse.rs	Exposes live and render title visibility in diagnostics.
src/​tree/​output.rs	Gates bar updates by visibility and narrows transaction damage.
src/​rect.rs	Handles empty rectangles in Rect::union.
src/​ifs/​wl_surface.rs	Simplifies surface extent unions.
src/​cursor.rs	Simplifies cursor damage extent unions.

_{Review effort: Balanced}