Hide local file link destinations in TUI markdown (#12705)

## Summary
- hide appended destinations for local path-style markdown links in the
TUI renderer
- keep web links rendering with their visible destination and style link
labels consistently
- add markdown renderer tests and a snapshot for the new file-link
output

## Testing
- just fmt
- cargo test -p codex-tui
<img width="1120" height="968" alt="image"
src="https://github.com/user-attachments/assets/490e8eda-ae47-4231-89fa-b254a1f83eed"
/>

codex-rs/tui/src/markdown_render.rs

@@ -85,6 +85,30 @@ pub(crate) fn render_markdown_text_with_width(input: &str, width: Option<usize>)
     w.text
 }
 
+#[derive(Clone, Debug)]
+struct LinkState {
+    destination: String,
+    show_destination: bool,
+}
+
+fn should_render_link_destination(dest_url: &str) -> bool {
+    !is_local_path_like_link(dest_url)
+}
+
+fn is_local_path_like_link(dest_url: &str) -> bool {
+    dest_url.starts_with("file://")
+        || dest_url.starts_with('/')
+        || dest_url.starts_with("~/")
+        || dest_url.starts_with("./")
+        || dest_url.starts_with("../")
+        || dest_url.starts_with("\\\\")
+        || matches!(
+            dest_url.as_bytes(),
+            [drive, b':', separator, ..]
+                if drive.is_ascii_alphabetic() && matches!(separator, b'/' | b'\\')
+        )
+}
+
 struct Writer<'a, I>
 where
     I: Iterator<Item = Event<'a>>,
@@ -95,7 +119,7 @@ where
     inline_styles: Vec<Style>,
     indent_stack: Vec<IndentContext>,
     list_indices: Vec<Option<u64>>,
-    link: Option<String>,
+    link: Option<LinkState>,
     needs_newline: bool,
     pending_marker_line: bool,
     in_paragraph: bool,
@@ -467,14 +491,21 @@ where
     }
 
     fn push_link(&mut self, dest_url: String) {
-        self.link = Some(dest_url);
+        self.push_inline_style(self.styles.link);
+        self.link = Some(LinkState {
+            show_destination: should_render_link_destination(&dest_url),
+            destination: dest_url,
+        });
     }
 
     fn pop_link(&mut self) {
         if let Some(link) = self.link.take() {
-            self.push_span(" (".into());
-            self.push_span(Span::styled(link, self.styles.link));
-            self.push_span(")".into());
+            self.pop_inline_style();
+            if link.show_destination {
+                self.push_span(" (".into());
+                self.push_span(Span::styled(link.destination, self.styles.link));
+                self.push_span(")".into());
+            }
         }
     }
 

codex-rs/tui/src/markdown_render_tests.rs

@@ -643,7 +643,7 @@ fn strong_emphasis() {
 fn link() {
     let text = render_markdown_text("[Link](https://example.com)");
     let expected = Text::from(Line::from_iter([
-        "Link".into(),
+        "Link".cyan().underlined(),
         " (".into(),
         "https://example.com".cyan().underlined(),
         ")".into(),
@@ -651,6 +651,46 @@ fn link() {
     assert_eq!(text, expected);
 }
 
+#[test]
+fn file_link_hides_destination() {
+    let text =
+        render_markdown_text("[markdown_render.rs:74](/Users/example/code/codex/codex-rs/tui/src/markdown_render.rs:74)");
+    let expected = Text::from(Line::from("markdown_render.rs:74".cyan().underlined()));
+    assert_eq!(text, expected);
+}
+
+#[test]
+fn url_link_shows_destination() {
+    let text = render_markdown_text("[docs](https://example.com/docs)");
+    let expected = Text::from(Line::from_iter([
+        "docs".cyan().underlined(),
+        " (".into(),
+        "https://example.com/docs".cyan().underlined(),
+        ")".into(),
+    ]));
+    assert_eq!(text, expected);
+}
+
+#[test]
+fn markdown_render_file_link_snapshot() {
+    let text = render_markdown_text(
+        "See [markdown_render.rs:74](/Users/example/code/codex/codex-rs/tui/src/markdown_render.rs:74).",
+    );
+    let rendered = text
+        .lines
+        .iter()
+        .map(|l| {
+            l.spans
+                .iter()
+                .map(|s| s.content.clone())
+                .collect::<String>()
+        })
+        .collect::<Vec<_>>()
+        .join("\n");
+
+    assert_snapshot!(rendered);
+}
+
 #[test]
 fn code_block_known_lang_has_syntax_colors() {
     let text = render_markdown_text("```rust\nfn main() {}\n```\n");

codex-rs/tui/src/snapshots/codex_tui__markdown_render__markdown_render_tests__markdown_render_file_link_snapshot.snap

@@ -0,0 +1,5 @@
+---
+source: tui/src/markdown_render_tests.rs
+expression: rendered
+---
+See markdown_render.rs:74.