fix: bill a Chat stream whose caller did not ask for usage - #34

… carried signatures

Cached input was billed at the full input price. The prompt count put
cache reads and writes together with plain input, so an Anthropic turn
that read 10k tokens from its cache cost as much as sending them fresh,
and weighed as much against rate limits and budgets. Models get three
optional weights against the input baseline: cache read, cache write,
and 1-hour cache write. Unset, they follow the input weight at
Anthropic's ratios (0.1x, 1.25x, 2x). Cost and weighted tokens now price
each bucket on its own weight. The audit row keeps the whole input in
`input_tokens` and gains the cache split in its detail. The admin API
and the model editor carry the new weights.

A request the upstream reported no usage for was billed as zero tokens.
#34 made Chat streams ask for usage, but usage can still be missing: the
upstream ignores `stream_options`, or the caller leaves mid-stream and
takes the final usage chunk with it. The count is now estimated at about
four bytes a token from the request and from the answer that arrived,
and the row says `usage_estimated`. A stream cut short keeps the
upstream's input count and bills the larger of its running output count
and the estimate. No answer at all still bills nothing.

A request forwarded as sent now drops the `tw1.` reasoning signatures an
earlier conversion wrote, via `tw_dialect::convert::strip_carried`, as
the desktop gateway does. Anthropic refuses a whole request over them.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

… carried signatures (#40)

Cached input was billed at the full input price. The prompt count put
cache reads and writes together with plain input, so an Anthropic turn
that read 10k tokens from its cache cost as much as sending them fresh,
and weighed as much against rate limits and budgets. Models get three
optional weights against the input baseline: cache read, cache write,
and 1-hour cache write. Unset, they follow the input weight at
Anthropic's ratios (0.1x, 1.25x, 2x). Cost and weighted tokens now price
each bucket on its own weight. The audit row keeps the whole input in
`input_tokens` and gains the cache split in its detail. The admin API
and the model editor carry the new weights.

A request the upstream reported no usage for was billed as zero tokens.
#34 made Chat streams ask for usage, but usage can still be missing: the
upstream ignores `stream_options`, or the caller leaves mid-stream and
takes the final usage chunk with it. The count is now estimated at about
four bytes a token from the request and from the answer that arrived,
and the row says `usage_estimated`. A stream cut short keeps the
upstream's input count and bills the larger of its running output count
and the estimate. No answer at all still bills nothing.

A request forwarded as sent now drops the `tw1.` reasoning signatures an
earlier conversion wrote, via `tw_dialect::convert::strip_carried`, as
the desktop gateway does. Anthropic refuses a whole request over them.

Co-authored-by: Claude Opus 5.5 <[email protected]>