feat: introduce --compute-indices flag to codex-file-search (#1419)

This is a small quality-of-life feature, the addition of
`--compute-indices` to the CLI, which, if enabled, will compute and set
the `indices` field for each `FileMatch` returned by `run()`. Note we
only bother to compute `indices` once we have the top N results because
there could be a lot of intermediate "top N" results during the search
that are ultimately discarded.

When set, the indices are included in the JSON output when `--json` is
specified and the matching indices are displayed in bold when `--json`
is not specified.

codex-rs/tui/src/file_search.rs

@@ -165,6 +165,7 @@ impl FileSearchManager {
         cancellation_token: Arc<AtomicBool>,
         search_state: Arc<Mutex<SearchState>>,
     ) {
+        let compute_indices = false;
         std::thread::spawn(move || {
             let matches = file_search::run(
                 &query,
@@ -173,11 +174,12 @@ impl FileSearchManager {
                 Vec::new(),
                 NUM_FILE_SEARCH_THREADS,
                 cancellation_token.clone(),
+                compute_indices,
             )
             .map(|res| {
                 res.matches
                     .into_iter()
-                    .map(|(_, p)| p)
+                    .map(|m| m.path)
                     .collect::<Vec<String>>()
             })
             .unwrap_or_default();