Show session ids in resume picker details

[fcoury-oai]

Why

PR #23234 updates the resume messaging for renamed threads to tell users to pick <name> (<thread-id>) from the resume picker, but the expanded picker details still hid the session id once a thread had a name.

That left a mismatch between the new guidance text and the picker UI. When duplicate thread names exist, the expanded Session: field should continue to expose the id so the user can verify they are about to resume the right session.

What Changed

• show <thread-name> (<thread-id>) in the resume picker Session: field when both values are available
• keep the existing fallback behavior for unnamed sessions or rows without an id
• update the existing picker rendering test to cover the combined session label

How to Test

1. Check out this branch on top of etraut/clarify-resume-hints.
2. Start Codex, create or resume a session, and rename it.
3. Open codex resume and expand the renamed session entry.
4. Confirm the Session: field shows <thread-name> (<thread-id>) instead of hiding the id.

Also verify that:

1. A session without a thread name still shows just the thread id in the Session: field.
2. The main row title in the picker is unchanged; this PR only updates the expanded details view.

Targeted tests:

• cargo test -p codex-tui expanded_session_details_include_metadata

Note: cargo test -p codex-tui still fails in this worktree because of an unrelated existing stack overflow in app::tests::discard_side_thread_removes_agent_navigation_entry.