feat: attest release tarballs with build provenance

[N4M3Z]

Problem

Module release tarballs published through module-release.yaml carry no provenance; nothing ties an asset on a GitHub release back to the workflow run and commit that built it.

Fix

actions/attest-build-provenance attests build/*.tar.gz after forge release, and the workflow declares the id-token and attestations permissions it needs. Consumers can verify assets with gh attestation verify.

Callers must grant the two new permissions in their release.yaml job, or the attestation step fails. Modules pinned to @main pick this requirement up on their next tag push; modules pinned to a tag (forge-core as of N4M3Z/forge-core#77) adopt it when they bump the pin, so tagging a v0.3.3 release after this merges gives them a clean target.

Test plan

• make validate green (clippy, tests, semgrep, forge validate, secret scan)
• Next module tag push produces a release with a verifiable attestation