Support contact clocks need immutable provider events, not a mutable issue contact field

Support contact clocks need immutable provider events, not a mutable issue contact field. This applies when help and stall rows can reopen or share a flow: build the trigger episode first, deduplicate provider objects, require same-episode linkage, and count accepted SMS or connected human calls before measuring response or completion. A contact timestamp equal to a help trigger can be a projection artifact, and a stopped projector makes no-linked-contact an unknown coverage state rather than a no-touch rate. This method does not establish causal support lift; driver-owned completion still needs a separate durable event.