rework patch/exec approval UI (#4573)

| Scenario | Screenshot |
| ---------------------- |
----------------------------------------------------------------------------------------------------------------------------------------------------
|
| short patch | <img width="1096" height="533" alt="short patch"
src="https://github.com/user-attachments/assets/8a883429-0965-4c0b-9002-217b3759b557"
/> |
| short command | <img width="1096" height="533" alt="short command"
src="https://github.com/user-attachments/assets/901abde8-2494-4e86-b98a-7cabaf87ca9c"
/> |
| long patch | <img width="1129" height="892" alt="long patch"
src="https://github.com/user-attachments/assets/fa799a29-a0d6-48e6-b2ef-10302a7916d3"
/> |
| long command | <img width="1096" height="892" alt="long command"
src="https://github.com/user-attachments/assets/11ddf79b-98cb-4b60-ac22-49dfa7779343"
/> |
| viewing complete patch | <img width="1129" height="892" alt="viewing
complete patch"
src="https://github.com/user-attachments/assets/81666958-af94-420e-aa66-b60d0a42b9db"
/> |

codex-rs/tui/src/render/mod.rs

@@ -1,2 +1,47 @@
+use ratatui::layout::Rect;
+
 pub mod highlight;
 pub mod line_utils;
+pub mod renderable;
+
+pub struct Insets {
+    pub left: u16,
+    pub top: u16,
+    pub right: u16,
+    pub bottom: u16,
+}
+
+impl Insets {
+    pub fn tlbr(top: u16, left: u16, bottom: u16, right: u16) -> Self {
+        Self {
+            top,
+            left,
+            bottom,
+            right,
+        }
+    }
+
+    pub fn vh(v: u16, h: u16) -> Self {
+        Self {
+            top: v,
+            left: h,
+            bottom: v,
+            right: h,
+        }
+    }
+}
+
+pub trait RectExt {
+    fn inset(&self, insets: Insets) -> Rect;
+}
+
+impl RectExt for Rect {
+    fn inset(&self, insets: Insets) -> Rect {
+        Rect {
+            x: self.x + insets.left,
+            y: self.y + insets.top,
+            width: self.width - insets.left - insets.right,
+            height: self.height - insets.top - insets.bottom,
+        }
+    }
+}