Render assistant file citations as local links (#42650)

## What changed

- Convert `codex-file-citation` directives in assistant Markdown into local-file links while preserving paths with Markdown-significant characters, Unicode, Windows separators, and location suffixes.
- Apply citation rendering consistently to streaming output, finalized messages and plans, and resume-picker transcript previews.
- Keep directives literal in code, HTML, existing links, reference definitions, escaped text, and generic Markdown rendering.
- Bound repeated parsing work for malformed directive candidates without limiting valid citations.

## Testing

- Add coverage for citation parsing and rendering across finalized, streaming, and resume-preview output, including malformed input and path edge cases.

GitOrigin-RevId: 5a0bfb3fc7ac21b7e8846fd170a349fb2d2d5e85

codex-rs/tui/src/markdown_render/streaming.rs

@@ -5,6 +5,7 @@
 
 use super::DecodedTextMerge;
 use super::Event;
+use super::FileCitations;
 use super::HyperlinkLine;
 use super::Options;
 use super::Parser;
@@ -38,10 +39,11 @@ pub(crate) fn render_streaming_markdown_lines_with_width_and_cwd(
     let mut options = Options::empty();
     options.insert(Options::ENABLE_STRIKETHROUGH);
     options.insert(Options::ENABLE_TABLES);
-    let parser = Parser::new_ext(input, options);
+    let citations = FileCitations::new(input, options);
+    let parser = Parser::new_ext(&citations.markdown, options);
     let has_reference_link_definition = parser.reference_definitions().iter().next().is_some();
     let parser = TopLevelBlockTracker {
-        iter: DecodedTextMerge::new(parser.into_offset_iter()),
+        iter: DecodedTextMerge::new(citations.events(parser, cwd)),
         depth: 0,
         block_count: 0,
         last_start: 0,