## Summary

Upgrade the L1 stateless-validator guests to [ERE
0.16.2](https://github.com/eth-act/ere/commit/8961a4e7ac5c9ca2dc6a2fc848452f23a186b1aa).

## Changes

- Update all stateless-validator ERE dependencies to
`8961a4e7ac5c9ca2dc6a2fc848452f23a186b1aa`.
- Upgrade the guest SDKs:
  - OpenVM: `v2.1.0-preview`
  - SP1: `v6.4.0`
  - ZisK: `v1.1.0-alpha`
- Update the SP1 patches and pin `openvm-eth` to the revisions used by
ERE 0.16.2.
- Remove obsolete OpenVM source patches.
- Keep Ethrex's OpenVM crypto provider and its canonical
field-serialization guard, while disabling ERE's default accelerator.
- Regenerate the stateless-validator and guest lockfiles.
- Update release artifact names, signing fixtures, and documentation.
- Update the release workflow to use ERE `0.16.2`.
- Remove the obsolete OpenVM Rust toolchain override.
- Pass ZisK's required `unaligned-scalar-mem` target feature during
compilation.

## Compatibility

This does not change RPC interfaces, SSZ schemas, or guest input/output
framing.

The upgrade produces new ELF and verification-key pairs for all three
zkVMs. Consumers must register the new VKs together with their
corresponding ELFs.

## Testing

- Locked Cargo metadata resolution for all four stateless-validator
workspaces.
- Stateless feature checks on Rust 1.93.
- OpenVM host crypto parity suite: 9 tests passed.
- EEST stateless fixture suite: 27,035 fixtures passed.
- Release version resolver, workflow lint, and signing guard tests.
- OpenVM, SP1, and ZisK container builds, key generation, and
conformance execution.