[TREAFREE]

Summary

Adds an opt-in setting that copies a successful one-input/one-output conversion to the macOS Clipboard for pasting into Finder or compatible apps.

Behavior

• defaults off to avoid replacing an existing Clipboard unexpectedly
• copies only a local ordinary output file when exactly one input produced exactly one output
• excludes multi-file batches and Split for Sharing results
• shows a compact Copied / 已复制 confirmation in the success summary
• keeps the AppKit pasteboard boundary injectable and isolated from SwiftUI
• documents the setting and corrects duplicate-build troubleshooting

Validation

• Swift Testing RED/GREEN coverage for the AppKit pasteboard writer and preference persistence
• IslandViewModel integration regression for a successful single-file conversion
• full macOS test suite: 415 passed, 0 failed, 0 skipped
• Release App build: passed
• FileIslandCLI universal build: passed
• Xcode static analysis: passed
• release packaging script: passed, including DMG layout, nested signatures, universal slices, FFmpeg/ffprobe audit, and AVFoundation helper smoke