chore(release): clean up mutable tag and ARM64-musl patch trail

[lodekeeper]

Parent tracker: ChainSafe/lodestar#9647
Origin: checkbox from the blst-z RC-readiness tracker.

Problem

The tracker flags tag hygiene problems around mutable zapi-v2.x.0 tags and the ARM64-musl patch trail. Mutable tags should not be used as release inputs, and the arm64-musl patch on nflaig/arm64-musl was flagged as hard to audit because the .hash did not change.

This issue tracks the lodestar-z side of cleaning up the tag/dependency trail before Lodestar consumes the package in an RC.

Acceptance Criteria

• Stop relying on mutable tags for release inputs; use immutable release tags or commit pins.
• Prune or replace stale mutable tag references where appropriate.
• Remove or supersede the arm64-musl patch from nflaig/arm64-musl with an auditable fix on top.
• Verify git fetch --prune --prune-tags leaves a clean, understandable dependency/tag state.
• Link any zapi-side follow-up needed for immutable release inputs.

References

• Tracking: blst-z (lodestar-z BLS + pubkey migration) — release-candidate readiness lodestar#9647
• feat: publish ARM64 musl bindings #482
• feat: support ARM64 musl targets zapi#47