Add seamless keyboard, mouse, and clipboard sharing

[Modole]

What changed

• add an input-only mode that lets the Mac mouse cross a configured display edge and control Windows without extending or streaming the screen
• add a macOS event-tap helper and a persistent Windows input-injection helper
• add draggable two-dimensional device layout, edge delay, automatic reconnect, and an emergency release shortcut
• add bidirectional plain-text clipboard synchronization with loop suppression
• advertise input, clipboard, and physical display capabilities in protocol v2
• retain the screen-permission refresh and auto-hiding receiver overlay fixes from the current working release
• package both native helpers and verify both universal2 slices in CI
• update the GUI, documentation, acceptance checklist, and troubleshooting guide

User impact

A single Mac keyboard and mouse can now control both the Mac desktop and a Windows computer by moving across the matching screen edge. The devices continue showing their own local desktops. Clipboard text follows the active workflow in either direction.

Validation

• npm test — 33 passing tests
• npm run dist:mac — universal2 DMG and ZIP built locally
• Windows x64 portable EXE and ZIP cross-built locally
• app binary, virtual-display helper, and input helper verified as x86_64 arm64
• macOS app passed deep strict code-signature verification
• DMG checksum verified with hdiutil verify
• GitHub Actions builds macOS and Windows artifacts from this branch

Remaining hands-on validation

The draft should be tested once on a real Windows 10/11 machine for Win32 input injection, DPI scaling, firewall behavior, and round-trip clipboard behavior before merging.