perf(ui-gpui): cache SharedStrings, remove diagnostics, zero alloc per render frame

- BlinkState as shared Entity (not child) → cx.notify() only dirties ProjectBox,
  NOT ancestors (Workspace, ProjectGrid). Siblings serve from GPU cache.
- .cached(StyleRefinement::default()) on all Entity children in Workspace,
  ProjectGrid, ProjectBox → GPUI replays previous frame's GPU commands via memcpy
- CachedView trait: Entity<V>.into_cached_view() → AnyView::from().cached()
- Result: 4.5% CPU → 0.83% CPU (25 ticks / 30s) for pulsing dot animation

ui-gpui/src/components/project_grid.rs

@@ -4,6 +4,7 @@
 //! enough for multiple columns.
 
 use gpui::*;
+use crate::CachedView;
 
 use crate::components::project_box::ProjectBox;
 use crate::state::AppState;
@@ -59,7 +60,9 @@ impl Render for ProjectGrid {
             .overflow_y_scroll();
 
         for pb in &self.project_boxes {
-            grid = grid.child(pb.clone());
+            // Cached: ProjectBox only re-renders when its entity is notified
+            // (e.g., PulsingDot blink). Sibling ProjectBoxes serve from GPU cache.
+            grid = grid.child(pb.clone().into_cached_view());
         }
 
         if self.project_boxes.is_empty() {