CRX files cannot be installed in modern Chrome without Chrome Web Store
publishing. Updated all docs to recommend 'Load unpacked' installation
method only. Added npm package loading method as alternative.
- Removed CRX build step from build-extension.yml workflow
- Removed CRX from artifact upload and release attachment
- Updated README.md, README.zh-CN.md, browser-bridge docs (en/zh)
- Added 'Load from npm package' as installation method