chore: refresh contract snapshot, /v1/cancel coverage test (#33)

* docs: add SDK defaults divergence notes to README

Document the actual retry, backoff, jitter, and timeout defaults of the Go, TypeScript, and Python SDKs with file and symbol references, so the drift between them is visible. No code defaults were changed.

* chore: refresh hawk daemon contract snapshot

Sync api/openapi.yaml to hawk main — drift since the last snapshot (110
lines of new endpoints) made the contract check fail on any PR.

* test: record support decisions for new /v1/cancel and /v1/metrics paths

The refreshed daemon contract snapshot added two endpoints; mark both
as explicitly unsupported (with reasons) so the coverage guard passes.

Author: Patel230