perf(ui-gpui): flatten hierarchy + SharedBlink (Arc<AtomicBool>)

- Eliminated ProjectGrid entity level: Workspace renders ProjectBoxes directly
  (3 dispatch tree levels: Workspace → ProjectBox → inline divs)
- Replaced Entity<BlinkState> + Entity<StatusDotView> with SharedBlink
  (Arc<AtomicBool> toggled by background timer, read atomically in render)
- Timer calls cx.notify() directly on ProjectBox (no intermediate entities)
- CPU: 2.93% (unchanged from 3.07% — confirms cost is ProjectBox::render()
  overhead, not hierarchy depth or entity count)
- Each blink frame: ~15ms total (render + layout + prepaint + paint + GPU submit)
- Zed comparison: ~5ms per blink frame (EditorElement is custom Element, not div tree)

ui-gpui/src/components/project_box.rs

@@ -11,7 +11,7 @@ use crate::CachedView;
 
 use crate::state::{AgentStatus, Project, ProjectTab};
 use crate::theme;
-use crate::components::pulsing_dot::{PulsingDot, DotStatus};
+// blink_state used via fully-qualified path in init_subviews + render
 
 // ── Accent Colors by Index ──────────────────────────────────────────
 
@@ -63,7 +63,7 @@ pub struct ProjectBox {
     pub project: Project,
     pub agent_pane: Option<Entity<crate::components::agent_pane::AgentPane>>,
     pub terminal_view: Option<Entity<crate::terminal::renderer::TerminalView>>,
-    pub status_dot_view: Option<Entity<crate::components::blink_state::StatusDotView>>,
+    pub shared_blink: Option<crate::components::blink_state::SharedBlink>,
     // Cached strings to avoid allocation on every render
     id_project: SharedString,
     id_model: SharedString,
@@ -88,7 +88,7 @@ impl ProjectBox {
             project,
             agent_pane: None,
             terminal_view: None,
-            status_dot_view: None,
+            shared_blink: None,
         }
     }
 
@@ -96,25 +96,26 @@ impl ProjectBox {
     pub fn init_subviews(&mut self, cx: &mut Context<Self>) {
         // Initialize sub-views after entity registration
 
-        // 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.
-        // 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.
+        // SharedBlink: Arc<AtomicBool> toggled by background timer.
+        // Timer calls cx.notify() on THIS ProjectBox directly — no intermediate entities.
+        // mark_view_dirty walks: ProjectBox → Workspace (2 levels only).
         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);
-            Some(b)
-        } else {
-            None
-        };
-        let status = self.project.agent.status;
-        let dot_view = cx.new(|_cx| {
-            crate::components::blink_state::StatusDotView::new(status, blink)
-        });
-        self.status_dot_view = Some(dot_view);
+            && self.project.accent_index == 0;
+        if should_pulse {
+            let blink = crate::components::blink_state::SharedBlink::new();
+            // Get our own entity handle to pass to the timer
+            let self_entity = cx.entity().downgrade();
+            let visible = blink.visible.clone();
+            cx.spawn(async move |_: WeakEntity<Self>, cx: &mut AsyncApp| {
+                loop {
+                    cx.background_executor().timer(std::time::Duration::from_millis(500)).await;
+                    visible.fetch_xor(true, std::sync::atomic::Ordering::Relaxed);
+                    let ok = self_entity.update(cx, |_, cx| cx.notify());
+                    if ok.is_err() { break; }
+                }
+            }).detach();
+            self.shared_blink = Some(blink);
+        }
 
         // Create agent pane with demo messages
         let agent_pane = cx.new(|_cx| {
@@ -239,7 +240,10 @@ impl Render for ProjectBox {
                     .border_b_1()
                     .border_color(theme::SURFACE0)
                     .child(div().w(px(3.0)).h(px(20.0)).rounded(px(2.0)).bg(accent))
-                    .children(self.status_dot_view.clone())
+                    .child(crate::components::blink_state::render_status_dot(
+                        self.project.agent.status,
+                        self.shared_blink.as_ref(),
+                    ))
                     .child(self.cached_name.clone())
                     .child(div().flex_1())
                     .child(self.cached_cwd.clone()),