chore(release): prepare 0.7.0 contract fixes

[moonyue-w]

Summary

Prepare version 0.7.0 for the contract fixes merged in #19. Align package metadata and move the completed changelog into 0.7.0, retaining budget and usage migration notes. Leave Unreleased empty for the next batch.

Why

The Managed budget request field changed from a monetary object to decimal-string max_credit_cost, requiring a minor release while pre-1.0. This batch also carries Session/SSE Credits, Identity ownership query parameters, and existing channel pairing corrections. Remaining existing-API contract updates are planned for 0.8.0; missing API endpoints are excluded.

Verification

• Version preparation checks: make check-version VERSION=0.7.0, go test ./convention.
• Changelog validation and 0.7.0 note extraction.
• Release automation unit tests: 19 passed.
• git diff --check.
• Full PR CI matrix and documentation checks passed before merge.
• Internal Build Test Package on the resulting main SHA, with run_live=true, run_sa=true, and sa_execution=true; CN/Global checks and artifact digests verified.

The merged feature PR has offline and targeted CN PAT live evidence. The candidate package also passed internal CN/Global integration and SA authentication/execution checks. Real channel pairing and compaction were not covered. The stable suites retain documented exclusions; automated checks do not constitute a human QA sign-off.

Impact

• Go, Python, and TypeScript release parity considered.
• Changelog and breaking-change migration notes retained.
• No credentials, live configuration, logs, or test output committed.

This PR changes release metadata only; public types, generated API docs, fixtures, and examples are unchanged. GitHub publication follows internal verification and the existing human Environment approval.

An initial CN Skill/Memory model-response assertion failed. An unchanged focused reproduction and one internal pipeline rerun passed; the initial failure record is retained. No assertion was weakened or skipped.