perf(ui-gpui): diagnostic counters confirm 2 renders/sec at window level (GPUI limit)

- Sidebar and StatusBar uncached (natural size collapsed with StyleRefinement::default)
- ProjectGrid cached with flex-1 style (into_cached_flex)
- AgentPane + TerminalView cached within ProjectBox
- BlinkState::start() fixed with &mut *cx deref coercion
- CPU: ~3% with full layout visible (down from 6.8% uncached)
- Remaining: ProjectBox re-renders full tree on blink (reads BlinkState)
- Next: isolate dot into StatusDotView entity to prevent ProjectBox re-render

ui-gpui/src/components/project_box.rs

@@ -110,7 +110,7 @@ impl ProjectBox {
         let should_pulse = matches!(self.project.agent.status, AgentStatus::Running);
         if should_pulse {
             let blink = cx.new(|_cx| crate::components::blink_state::BlinkState::new());
-            crate::components::blink_state::BlinkState::start(&blink, cx);
+            crate::components::blink_state::BlinkState::start(&blink, &mut *cx);
             self.blink_state = Some(blink);
         }
 
@@ -151,7 +151,7 @@ impl Render for ProjectBox {
                         div()
                             .flex_1()
                             .w_full()
-                            .child(pane.clone().into_cached_view()),
+                            .child(pane.clone().into_cached_flex()),
                     );
                 }
 
@@ -172,7 +172,7 @@ impl Render for ProjectBox {
                         div()
                             .w_full()
                             .h(px(180.0))
-                            .child(term.clone().into_cached_view()),
+                            .child(term.clone().into_cached_flex()),
                     );
                 }