createTimelineSlotBinding

Description#

The family-standard three-stage template cascade, as one named concept:

instance contentChild  ->  CNGX_*_CONFIG.templates.<key>  ->  null

The contentChild() query itself has to stay a direct field initialiser on the component (AOT rejects it from a helper, NG8110), but resolving the three tiers does not - and writing that resolution out once per slot turns a single rule into eight places it can drift.

configured is a thunk rather than a value so the config tier is read at resolution time, inside the computed().

Exported because an ejected skin resolves the same three tiers and would otherwise have to restate the rule.