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/cli/src/main.rs

@@ -38,6 +38,7 @@ use codex_tui::UpdateAction;
 use codex_utils_absolute_path::AbsolutePathBuf;
 use codex_utils_cli::CliConfigOverrides;
 use codex_utils_cli::ProfileV2Name;
+use codex_utils_cli::resume_command;
 use owo_colors::OwoColorize;
 use std::io::IsTerminal;
 use std::path::PathBuf;
@@ -628,9 +629,7 @@ fn format_exit_messages(exit_info: AppExitInfo, color_enabled: bool) -> Vec<Stri
         lines.push(token_usage.to_string());
     }
 
-    if let Some(resume_cmd) =
-        codex_core::util::resume_command(/*thread_name*/ None, conversation_id)
-    {
+    if let Some(resume_cmd) = resume_command(/*thread_name*/ None, conversation_id) {
         let command = if color_enabled {
             resume_cmd.cyan().to_string()
         } else {