chore: bump version to v2026.4.305 and update changelog}
- Bump version from v2026.4.304 to v2026.4.305 in package.json
- Add v2026.4.305 changelog entry with OnPush change detection refactor, webpack optimization simplification, Angular Linker AOT support, and production runtime chunk fix
- Update build version footer across README, artifacts, changelogs, and contributors docs