feat: align UEC Envelope 1.0 + update all adapters

[m2papierz]

Summary

This PR hardens the UEC format by aligning UEC models with the JSON schemas (Envelope 1.0) and updates all adapters to emit the new, consistent envelopes. It fixes schema/version/file mismatches, standardizes producer metadata, synchronizes snapshot schema_versions, and unifies artifact references across engine and adapters so validation is reliable and stored envelopes remain comparable. Adapters were updated to emit canonicalized results and consistent device/program/execution snapshots under the new contract.

Type of change

• Bug fix
• New feature
• Refactor (no user-facing change)
• Docs only
• CI/build tooling
• Breaking change

Changelog (user-facing only)

• I added a towncrier fragment in changelog.d/

Checklist

• I ran lint locally (uv run pre-commit run --all-files)
• I ran tests locally (uv run pytest)
• I added/updated tests for behavior changes
• I updated docs/README/examples if needed
• If I changed dependencies, I updated uv.lock (uv lock) and committed it
• I considered backward compatibility and security impact

Notes for reviewers

• Breaking format change: adapters now emit Envelope 1.0 / updated snapshot versions.

All adapters were updated to:

• emit producer consistently (adapter + sdk + versions),
• produce synchronized device/program/execution snapshot versions,
• use unified ArtifactRef shape,
• keep results comparable via canonicalization metadata.