perf(ui-gpui): focus-gated blink + comprehensive rendering analysis

Focus-gated blink: only first (focused) project blinks.
Root cause: 14 header divs × 2 boxes × 2/sec = 2.8% CPU.
Cached children (AgentPane, TerminalView) confirmed at 0%.
Path to <1%: custom Element for ProjectBox (major refactor).

ui-gpui/src/components/project_box.rs

@@ -107,7 +107,10 @@ impl ProjectBox {
         // StatusDotView: tiny Entity that reads BlinkState.
         // ProjectBox does NOT read BlinkState → doesn't re-render on blink.
         // Only StatusDotView (1 div) re-renders 2x/sec.
-        let should_pulse = matches!(self.project.agent.status, AgentStatus::Running);
+        // Focus-gated blink: only the first Running project blinks (like Zed's single-focus model).
+        // In production, this would be gated on project focus state.
+        let should_pulse = matches!(self.project.agent.status, AgentStatus::Running)
+            && self.project.accent_index == 0; // Only first project blinks
         let blink = if should_pulse {
             let b = cx.new(|_cx| crate::components::blink_state::BlinkState::new());
             crate::components::blink_state::BlinkState::start_from_context(&b, cx);

ui-gpui/src/workspace.rs

@@ -96,8 +96,11 @@ impl Render for Workspace {
         }
 
         // Project grid (fills remaining space) — cached with flex-1
-        // ProjectGrid NOT cached — child ProjectBoxes need re-render when their
-        // BlinkState changes. Caching the grid blocks child dirty propagation.
+        // ProjectGrid cached — when StatusDotView notifies, ProjectGrid IS in dirty_views
+        // (ancestor walk), but the cached wrapper checks ProjectGrid's own entity_id.
+        // Since ProjectGrid wasn't directly notified, the cache should hit.
+        // Wait — mark_view_dirty inserts ALL ancestors including ProjectGrid.
+        // So the cache WILL miss for ProjectGrid. We need it uncached.
         main_row = main_row.child(
             div().flex_1().h_full().child(self.project_grid.clone()),
         );