fix: the 7 omitted lines issue (#5141)

Before, the CLI was always showing `... +7 lines` (with the 7 constant)
due to a double truncation

<img width="263" height="127" alt="Screenshot 2025-10-13 at 10 28 11"
src="https://github.com/user-attachments/assets/49a92d2b-c28a-4e2f-96d1-1818955470b8"
/>

codex-rs/tui/src/chatwidget/snapshots/codex_tui__chatwidget__tests__binary_size_ideal_response.snap

@@ -1,6 +1,5 @@
 ---
 source: tui/src/chatwidget/tests.rs
-assertion_line: 1152
 expression: "lines[start_idx..].join(\"\\n\")"
 ---
 • I need to check the codex-rs repository to explain why the project's binaries
@@ -33,7 +32,7 @@ expression: "lines[start_idx..].join(\"\\n\")"
   │ … +1 lines
   └ --- ansi-escape/Cargo.toml
     [package]
-    … +7 lines
+    … +243 lines
     ] }
     tracing = { version