feat: add support for file_opener option in Rust, similiar to #911 (#957)

This ports the enhancement introduced in
https://github.com/openai/codex/pull/911 (and the fixes in
https://github.com/openai/codex/pull/919) for the TypeScript CLI to the
Rust one.

codex-rs/tui/src/citation_regex.rs

@@ -0,0 +1,22 @@
+#![allow(clippy::expect_used)]
+
+use regex::Regex;
+
+// This is defined in its own file so we can limit the scope of
+// `allow(clippy::expect_used)` because we cannot scope it to the `lazy_static!`
+// macro.
+lazy_static::lazy_static! {
+    /// Regular expression that matches Codex-style source file citations such as:
+    ///
+    /// ```text
+    /// 【F:src/main.rs†L10-L20】
+    /// ```
+    ///
+    /// Capture groups:
+    /// 1. file path (anything except the dagger `†` symbol)
+    /// 2. start line number (digits)
+    /// 3. optional end line (digits or `?`)
+    pub(crate) static ref CITATION_REGEX: Regex = Regex::new(
+        r"【F:([^†]+)†L(\d+)(?:-L(\d+|\?))?】"
+    ).expect("failed to compile citation regex");
+}