* fix(cost): honor per-second custom pricing on chat completions for every provider
* test(cost): assert a per-second priced deployment bills instead of staying at $0
The zero-cost diagnostic tests from #42345 used a per-second-only entry as their
misconfigured fixture, which this branch now bills. Switch that fixture to a
per-query-only entry, which is still selected as the deployment's own pricing and
still prices chat usage at $0, and add a per-second test asserting the call
duration is billed with no diagnostic
Also let a caller's explicit total_time outrank the logging window in
completion_cost, so the SDK precedence stays stamped response, caller, logging
* test(response_metadata): move the per-second pricing regression into the mapped tests/unit file
* fix(cost_calculator): keep media-mode per-second rates off the wall-clock path
A video, transcription, speech, or realtime entry's per-second rates price media seconds, which
their dedicated cost paths bill from the media itself. The generic per-second branch now skips
those modes, so a video status poll on a per-second video model bills nothing instead of the
seconds the poll took to answer.
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Co-authored-by: mateo-berri <277851410+mateo-berri@users.noreply.github.com>
