fix(tui/animation): ensure intro logo visibly completes without perf cost

- Remove per-frame debug log in intro renderer
- Delay internal fade to last ~2% and force final frame vivid
- Defer any fade-out to AnimatedWelcomeCell alpha blending

Keeps animation smooth and visually complete on all terminals.

codex-rs/tui/src/glitch_animation.rs

@@ -5,7 +5,8 @@ use ratatui::widgets::Widget;
 
 // Render the outline-fill animation
 pub fn render_intro_animation(area: Rect, buf: &mut Buffer, t: f32) {
-    tracing::debug!("render_intro_animation called: area={:?}, t={}", area, t);
+    // Avoid per-frame debug logging here to keep animation smooth.
+    // (Heavy logging can starve the render loop on slower terminals.)
     render_intro_outline_fill(area, buf, t)
 }
 
@@ -31,7 +32,10 @@ pub fn render_intro_outline_fill(area: Rect, buf: &mut Buffer, t: f32) {
     let t = t.clamp(0.0, 1.0);
     let outline_p = smoothstep(0.00, 0.60, t); // outline draws L->R
     let fill_p = smoothstep(0.35, 0.95, t); // interior fills L->R
-    let fade = smoothstep(0.90, 1.00, t); // vibrant -> muted gray
+    // Keep the animation vivid until the very end. Only begin a subtle fade in
+    // the last ~2% of progress, and render the final frame fully bright.
+    let mut fade = smoothstep(0.98, 1.00, t);
+    if (t - 1.0).abs() < 1e-6 { fade = 0.0; }
     let scan_p = smoothstep(0.55, 0.85, t); // scanline sweep
     let frame = (t * 60.0) as u32;
 
@@ -91,7 +95,11 @@ pub fn render_intro_outline_fill_with_alpha(area: Rect, buf: &mut Buffer, t: f32
     let alpha = alpha.clamp(0.0, 1.0);
     let outline_p = smoothstep(0.00, 0.60, t); // outline draws L->R
     let fill_p = smoothstep(0.35, 0.95, t); // interior fills L->R
-    let fade = smoothstep(0.90, 1.00, t); // vibrant -> muted gray
+    // Match the non-alpha path: keep vivid until the end and avoid dimming the
+    // terminal-stable final frame. Any longer fade-out is handled by the caller
+    // (AnimatedWelcomeCell) using alpha blending.
+    let mut fade = smoothstep(0.98, 1.00, t);
+    if (t - 1.0).abs() < 1e-6 { fade = 0.0; }
     let scan_p = smoothstep(0.55, 0.85, t); // scanline sweep
     let frame = (t * 60.0) as u32;