DI token a host provides on itself when content-projected
CngxOption instances need a fallback path to highlight + activate
hover behaviour. Mirrors the four other shell-host tokens
(CNGX_OPTION_CONTAINER, CNGX_OPTION_STATUS_HOST,
CNGX_OPTION_FILTER_HOST, CNGX_SELECT_SHELL_SEARCH_HOST).
CngxOption injects this token with { optional: true } -
standalone use (no host provides the token) leaves option behaviour
unchanged because the option's own AD inject takes precedence when
available.