Trim TUI legacy core helper usage (#22695)

## Why

The TUI still had a few low-risk dependencies flowing through the
transitional `legacy_core` namespace after the app-server migration.
These helpers either already have clearer non-core owners or are
presentation logic that does not belong in `codex-core`, so moving them
out reduces the compatibility surface without changing product behavior.

## What changed

This is a low-risk change, almost completely mechanical in nature.

- Route TUI Codex-home lookup through `codex-utils-home-dir`, use
`Config::log_dir` directly, and call
`codex-sandboxing::system_bwrap_warning` without going through
`legacy_core`.
- Move shared `codex resume` hint formatting from `codex-core` into
`codex-utils-cli`.
- Update CLI and TUI call sites to use the shared CLI utility, and keep
the resume-command behavior covered by tests in its new home.

## Verification

- `cargo test -p codex-utils-cli`
- `cargo test -p codex-utils-cli resume_command`

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

@@ -1,6 +1,7 @@
 mod approval_mode_cli_arg;
 mod config_override;
 pub(crate) mod format_env_display;
+mod resume_command;
 mod sandbox_mode_cli_arg;
 mod shared_options;
 
@@ -8,5 +9,6 @@ pub use approval_mode_cli_arg::ApprovalModeCliArg;
 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 sandbox_mode_cli_arg::SandboxModeCliArg;
 pub use shared_options::SharedCliOptions;

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

@@ -0,0 +1,64 @@
+//! Shared formatting for user-facing `codex resume` command hints.
+
+use codex_protocol::ThreadId;
+use codex_shell_command::parse_command::shlex_join;
+
+pub fn resume_command(thread_name: Option<&str>, thread_id: Option<ThreadId>) -> Option<String> {
+    let resume_target = thread_name
+        .filter(|name| !name.is_empty())
+        .map(str::to_string)
+        .or_else(|| thread_id.map(|thread_id| thread_id.to_string()));
+    resume_target.map(|target| {
+        let needs_double_dash = target.starts_with('-');
+        let escaped = shlex_join(&[target]);
+        if needs_double_dash {
+            format!("codex resume -- {escaped}")
+        } else {
+            format!("codex resume {escaped}")
+        }
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use pretty_assertions::assert_eq;
+
+    #[test]
+    fn prefers_name_over_id() {
+        let thread_id = ThreadId::from_string("123e4567-e89b-12d3-a456-426614174000").unwrap();
+        let command = resume_command(Some("my-thread"), Some(thread_id));
+        assert_eq!(command, Some("codex resume my-thread".to_string()));
+    }
+
+    #[test]
+    fn formats_thread_id_when_name_is_missing() {
+        let thread_id = ThreadId::from_string("123e4567-e89b-12d3-a456-426614174000").unwrap();
+        let command = resume_command(/*thread_name*/ None, Some(thread_id));
+        assert_eq!(
+            command,
+            Some("codex resume 123e4567-e89b-12d3-a456-426614174000".to_string())
+        );
+    }
+
+    #[test]
+    fn returns_none_without_a_resume_target() {
+        let command = resume_command(/*thread_name*/ None, /*thread_id*/ None);
+        assert_eq!(command, None);
+    }
+
+    #[test]
+    fn quotes_thread_names_when_needed() {
+        let command = resume_command(Some("-starts-with-dash"), /*thread_id*/ None);
+        assert_eq!(
+            command,
+            Some("codex resume -- -starts-with-dash".to_string())
+        );
+
+        let command = resume_command(Some("two words"), /*thread_id*/ None);
+        assert_eq!(command, Some("codex resume 'two words'".to_string()));
+
+        let command = resume_command(Some("quote'case"), /*thread_id*/ None);
+        assert_eq!(command, Some("codex resume \"quote'case\"".to_string()));
+    }
+}