fix(release): make the public bundle releasable

[rldyourmnd]

Summary

• run release validation in one job-scoped hash-locked Python virtual environment
• add the missing canonical gds-drakkars plugin source declared by the registry
• print redirected JSON when a Go-core validator fails
• record the completed 0.1.2 release fixes in the changelog

Root causes proven by runs

• run 32686874258: release job lacked Python dependencies
• run 32687772251: full validation reached validate plugins, which failed because plugins/gds-drakkars did not exist; the redirected JSON made the gate silent

Verification

• plugin-creator validate_plugin.py plugins/gds-drakkars
• gds --json validate plugins
• go test ./core/releasebuilder
• scripts/validate_go_core.sh --quick
• clean detached worktree with job-scoped venv: scripts/validate_release.sh
• full race/cross-build, 42 Python tests, integrated 2000-repository assurance: PASS
• actionlint .github/workflows/release-bundle.yml
• git diff --check