fix: patch subagent display (#512)

Co-authored-by: Letta <noreply@letta.com>

src/cli/contexts/AnimationContext.tsx

@@ -0,0 +1,54 @@
+/**
+ * AnimationContext - Global context for controlling animations based on overflow
+ *
+ * When the live content area exceeds the terminal viewport, Ink's clearTerminal
+ * behavior causes severe flickering on every re-render. This context provides
+ * a global `shouldAnimate` flag that components (like BlinkDot) can consume
+ * to disable animations when content would overflow.
+ *
+ * The parent (App.tsx) calculates total live content height and determines
+ * if animations should be disabled, then provides this via context.
+ */
+
+import { createContext, type ReactNode, useContext } from "react";
+
+interface AnimationContextValue {
+  /**
+   * Whether animations should be enabled.
+   * False when live content would overflow the viewport.
+   */
+  shouldAnimate: boolean;
+}
+
+const AnimationContext = createContext<AnimationContextValue>({
+  shouldAnimate: true,
+});
+
+/**
+ * Hook to access the animation context.
+ * Returns { shouldAnimate: true } if used outside of a provider.
+ */
+export function useAnimation(): AnimationContextValue {
+  return useContext(AnimationContext);
+}
+
+interface AnimationProviderProps {
+  children: ReactNode;
+  shouldAnimate: boolean;
+}
+
+/**
+ * Provider component that controls animation state for all descendants.
+ * Wrap the live content area with this and pass shouldAnimate based on
+ * overflow detection.
+ */
+export function AnimationProvider({
+  children,
+  shouldAnimate,
+}: AnimationProviderProps) {
+  return (
+    <AnimationContext.Provider value={{ shouldAnimate }}>
+      {children}
+    </AnimationContext.Provider>
+  );
+}