Dismiss, keeping a terminal default chosen this session or restoring.
Pressing t to save a per-terminal default is a deliberate choice, so
Esc keeps that theme instead of reverting. action_set_for_terminal
records the choice synchronously (and clears it only if the async save
fails), so Esc keeps the theme even when the write is still in flight;
the persisted [ui.terminal_themes] mapping is the source of truth
across sessions. dismiss(None) intentionally skips the global
[ui].theme write. Without a t press — or after a failed save — Esc
restores the theme that was active when the picker opened.
