fix(release): sync product contract version

[vntrevx]

Root cause

The v1.6.1 package metadata was updated, but .github/product-release-contract.json still declared 1.6.0. The candidate sealing job therefore failed its exact package-version contract before hashing assets.

Fix

• synchronize the product release contract to 1.6.1
• assert the contract version always equals pyproject.toml

Evidence

• reproduced the workflow jq condition returning false before the fix and true after it
• uv run pytest -q tests/test_release_contract.py::test_product_release_workflows_preserve_non_combined_boundary tests/test_update.py tests/test_cli.py (23 passed)
• uv run ruff check tests/test_release_contract.py

[chatgpt-codex-connector]

You have reached your Codex usage limits for code reviews. You can see your limits in the Codex usage dashboard.