v4.0.0-rc.12

chore: release rc.11 and fix gem publishing

- Update Cargo.toml and all manifests to version 4.0.0-rc.11
- Fix Ruby gem publishing: removed broken manual compression that was double-gzipping valid gems
  Root cause: gems are POSIX tar archives with gzipped internal files (standard RubyGems format)
  gem spec validation now passes directly on build output
- Fix version sync script: corrected regex pattern for Go module version extraction
- Run full update and lint suite - all checks passing

v4.0.0-rc.9