feat: standalone file search CLI (#1386)

Standalone fuzzy filename search library that should be helpful in
addressing https://github.com/openai/codex/issues/1261.

codex-rs/justfile

@@ -16,6 +16,10 @@ exec *args:
 tui *args:
     cargo run --bin codex -- tui "$@"
 
+# Run the CLI version of the file-search crate.
+file-search *args:
+    cargo run --bin codex-file-search -- "$@"
+
 # format code
 fmt:
     cargo fmt -- --config imports_granularity=Item