Responses reasoning emitted only in response.output_item.done was ignored
until a later token or terminal event. Count non-empty summary and content
text in the shared classifier while excluding empty and encrypted-only
items.
Add deterministic coverage for Meta Responses and Claude downstreams,
classification boundaries, and preservation of an earlier token time.
Refresh the bootstrap-buffering comment to match the shared helper.
Refs #6664
Meta streaming armed protocol-aware TTFT tracking but never observed token
events, so usage records kept the first-body-byte fallback even when
substantive output arrived later. Observe Responses events before failure
publication and translation using the existing shared helper.
Add deterministic virtual-clock coverage for content, terminal events,
error fallbacks, downstream translation, and non-streaming timing.
Fixes#6664