Fix release.yml and prepare 1.2.3

[bitterpanda63]

Summary

• Bumps rubygems/release-gem from v1.0.0 (a25424ba2ba8b387abc8ef40807c2c85b96cbe32) to v1.2.0 (6317d8d1f7e28c24d28f6eff169ea854948bd9f7) to fix Unsupported key type PKIX_ED25519 errors from the bundled sigstore-cli when pushing gems with attestation. Fixed upstream in v1.1.2 (sigstore-cli update).
• Bumps aikido-zen to v1.2.3 across lib/aikido/zen/version.rb and all 24 *.gemfile.lock files.

Why 1.2.3 and not re-release 1.2.2

The v1.2.2 release partially published: 7 of 8 platform gems pushed (fallback path after attestation failure), but x86_64-mingw-64 and the platform-agnostic ruby gem never made it to RubyGems. Per .github/RELEASE.md troubleshooting ("bump to X.Y.Z+1 and re-release rather than fighting it"), 1.2.3 is the clean path.

Test plan

• CI green (unit tests, lint, e2e)
• After merge: gh release create v1.2.3 --target main --title v1.2.3 … and confirm all 8 platform gems + the ruby gem land on rubygems.org with no PKIX_ED25519 errors in the workflow log

Summary by Aikido

Security Issues: 0	Quality Issues: 0	Resolved Issues: 0

⚡ Enhancements

• Bumped gem VERSION to 1.2.3 preparing new release

🐛 Bugfixes

• Updated rubygems/release-gem action to v1.2.0 to fix attestation

^{More info}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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