Math Chords 0.1.6

Changed

• Drop deprecated main field from manifest.json (Obsidian loads main.js by default).
• GitHub Releases now attach artifact attestations for main.js and styles.css.
• Release assets are only main.js, manifest.json, and styles.css (no zip bundle).
• Sync README, README.zh-CN, .cursorrules, and package-lock.json to v0.1.6.