tui: fix approval dialog for large commands (#3087)

#### Summary
- Emit a “Proposed Command” history cell when an ExecApprovalRequest
arrives (parity with proposed patches).
- Simplify the approval dialog: show only the reason/instructions; move
the command preview into history.
- Make approval/abort decision history concise:
  - Single line snippet; if multiline, show first line + " ...".
  - Truncate to 80 graphemes with ellipsis for very long commands.

#### Details
- History
- Add `new_proposed_command` to render a header and indented command
preview.
  - Use shared `prefix_lines` helper for first/subsequent line prefixes.
- Approval UI
- `UserApprovalWidget` no longer renders the command in the modal; shows
optional `reason` text only.
  - Decision history renders an inline, dimmed snippet per rules above.
- Tests (snapshot-based)
  - Proposed/decision flow for short command.
  - Proposed multi-line + aborted decision snippet with “ ...”.
  - Very long one-line command -> truncated snippet with “…”.
  - Updated existing exec approval snapshots and test reasons.

<img width="1053" height="704" alt="Screenshot 2025-09-03 at 11 57
35 AM"
src="https://github.com/user-attachments/assets/9ed4c316-9daf-4ac1-80ff-7ae1f481dd10"
/>

after approving:

<img width="1053" height="704" alt="Screenshot 2025-09-03 at 11 58
18 AM"
src="https://github.com/user-attachments/assets/a44e243f-eb9d-42ea-87f4-171b3fb481e7"
/>

rejection:

<img width="1053" height="207" alt="Screenshot 2025-09-03 at 11 58
45 AM"
src="https://github.com/user-attachments/assets/a022664b-ae0e-4b70-a388-509208707934"
/>

big command:


https://github.com/user-attachments/assets/2dd976e5-799f-4af7-9682-a046e66cc494

codex-rs/tui/src/history_cell.rs

@@ -2,6 +2,7 @@ use crate::diff_render::create_diff_summary;
 use crate::exec_command::relativize_to_home;
 use crate::exec_command::strip_bash_lc_and_escape;
 use crate::markdown::append_markdown;
+use crate::render::line_utils::prefix_lines;
 use crate::slash_command::SlashCommand;
 use crate::text_formatting::format_and_truncate_tool_result;
 use base64::Engine;
@@ -1140,33 +1141,9 @@ impl HistoryCell for PlanUpdateCell {
                 .into_iter()
                 .map(|s| s.to_string().set_style(step_style).into())
                 .collect();
-            prefix_lines(step_text, &box_str.into(), &"  ".into())
+            prefix_lines(step_text, box_str.into(), "  ".into())
         };
 
-        fn prefix_lines(
-            lines: Vec<Line<'static>>,
-            initial_prefix: &Span<'static>,
-            subsequent_prefix: &Span<'static>,
-        ) -> Vec<Line<'static>> {
-            lines
-                .into_iter()
-                .enumerate()
-                .map(|(i, l)| {
-                    Line::from(
-                        [
-                            vec![if i == 0 {
-                                initial_prefix.clone()
-                            } else {
-                                subsequent_prefix.clone()
-                            }],
-                            l.spans,
-                        ]
-                        .concat(),
-                    )
-                })
-                .collect()
-        }
-
         let mut lines: Vec<Line<'static>> = vec![];
         lines.push(vec!["• ".into(), "Updated Plan".bold()].into());
 
@@ -1187,7 +1164,7 @@ impl HistoryCell for PlanUpdateCell {
                 indented_lines.extend(render_step(status, step));
             }
         }
-        lines.extend(prefix_lines(indented_lines, &"  └ ".into(), &"    ".into()));
+        lines.extend(prefix_lines(indented_lines, "  └ ".into(), "    ".into()));
 
         lines
     }
@@ -1231,6 +1208,26 @@ pub(crate) fn new_patch_apply_failure(stderr: String) -> PlainHistoryCell {
     PlainHistoryCell { lines }
 }
 
+/// Create a new history cell for a proposed command approval.
+/// Renders a header and the command preview similar to how proposed patches
+/// show a header and summary.
+pub(crate) fn new_proposed_command(command: &[String]) -> PlainHistoryCell {
+    let cmd = strip_bash_lc_and_escape(command);
+
+    let mut lines: Vec<Line<'static>> = Vec::new();
+    lines.push(Line::from(vec!["• ".into(), "Proposed Command".bold()]));
+
+    let cmd_lines: Vec<Line<'static>> = cmd
+        .lines()
+        .map(|part| Line::from(part.to_string()))
+        .collect();
+    let initial_prefix: Span<'static> = "  └ ".dim();
+    let subsequent_prefix: Span<'static> = "    ".into();
+    lines.extend(prefix_lines(cmd_lines, initial_prefix, subsequent_prefix));
+
+    PlainHistoryCell { lines }
+}
+
 pub(crate) fn new_reasoning_block(
     full_reasoning_buffer: String,
     config: &Config,