v1.6 — Firefox clipboard fix & code cleanup

• Fixed clipboard writing on Firefox: clipboard.write() is now initiated synchronously during the user click gesture using a deferred Promise<Blob>, so it no longer fails due to missing user activation
• Removed unused clipboard bridge code from injector.ts
• Removed unnecessary clipboardWrite permission — clipboard is handled in MAIN world via user gesture
• Deduplicated HTML encoding logic between toolbar.ts and the capture library