v0.6.1: stopped runs are billed in full

A fix for the Go runtime. Go module github.com/eadwinCode/agentic-kit/packages/go-agentenkit@v0.6.1, npm agentenkit@0.6.1 and use-agentenkit@0.6.1.

No breaking changes.

Fixed (#24)

• Before: a stop that landed after the provider answered, but before the call was priced, could make a pricer that reads a price list fail with context canceled. The paid call was then stored unpriced, so it was never billed.
• Now: Go prices a usage row on a context a stop cannot cancel, as it already did for the write.
• Covered: every call: steps of the main run and nested runs, compaction passes and tool calls.
• TS: already behaved this way. Its pricer is never given a signal.