Clarify resume hints for renamed threads (#23234)

Addresses #23181

## Why
Renamed threads can share names, so hints that suggest resuming directly
by name are ambiguous. Issue #23181 asks for the picker hint to include
the thread name and thread ID in parens so users can disambiguate
safely.

## What
- Adds a shared resume hint formatter for named threads: run `codex
resume`, then select `<name> (<thread-id>)`.
- Uses that hint for /rename confirmations, TUI session summaries, and
CLI/TUI exit messages.
- Keeps direct `codex resume <thread-id>` guidance for unnamed threads.

## Verification
Manually verified that message after `/rename` and after `/exit` include
session ID in parens.

---------

Co-authored-by: Felipe Coury <felipe.coury@openai.com>

codex-rs/utils/cli/src/lib.rs

@@ -10,5 +10,6 @@ pub use codex_protocol::config_types::ProfileV2Name;
 pub use config_override::CliConfigOverrides;
 pub use format_env_display::format_env_display;
 pub use resume_command::resume_command;
+pub use resume_command::resume_hint;
 pub use sandbox_mode_cli_arg::SandboxModeCliArg;
 pub use shared_options::SharedCliOptions;

codex-rs/utils/cli/src/resume_command.rs

@@ -19,6 +19,16 @@ pub fn resume_command(thread_name: Option<&str>, thread_id: Option<ThreadId>) ->
     })
 }
 
+pub fn resume_hint(thread_name: Option<&str>, thread_id: Option<ThreadId>) -> Option<String> {
+    let thread_id = thread_id?;
+    match thread_name.filter(|name| !name.is_empty()) {
+        Some(thread_name) => Some(format!(
+            "codex resume, then select {thread_name} ({thread_id})"
+        )),
+        None => resume_command(/*thread_name*/ None, Some(thread_id)),
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -61,4 +71,33 @@ mod tests {
         let command = resume_command(Some("quote'case"), /*thread_id*/ None);
         assert_eq!(command, Some("codex resume \"quote'case\"".to_string()));
     }
+
+    #[test]
+    fn resume_hint_names_picker_item_with_id() {
+        let thread_id = ThreadId::from_string("123e4567-e89b-12d3-a456-426614174000").unwrap();
+        let hint = resume_hint(Some("my-thread"), Some(thread_id));
+        assert_eq!(
+            hint,
+            Some(
+                "codex resume, then select my-thread (123e4567-e89b-12d3-a456-426614174000)"
+                    .to_string()
+            )
+        );
+    }
+
+    #[test]
+    fn resume_hint_uses_direct_id_command_without_name() {
+        let thread_id = ThreadId::from_string("123e4567-e89b-12d3-a456-426614174000").unwrap();
+        let hint = resume_hint(/*thread_name*/ None, Some(thread_id));
+        assert_eq!(
+            hint,
+            Some("codex resume 123e4567-e89b-12d3-a456-426614174000".to_string())
+        );
+    }
+
+    #[test]
+    fn resume_hint_requires_thread_id() {
+        let hint = resume_hint(Some("my-thread"), /*thread_id*/ None);
+        assert_eq!(hint, None);
+    }
 }