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;