✨ Add Windows native lazy file clipboard write via JNA delayed rendering

[guiyanakuang]

Summary

• Add WindowsLazyClipboard class implementing Windows delayed rendering for file-type clipboard data via JNA, mirroring the macOS NSPasteboardItemDataProvider approach (PR Add macOS native lazy file pasteboard write via NSPasteboardItemDataProvider #3930)
• Add WM_RENDERFORMAT / WM_RENDERALLFORMATS constants and RegisterClipboardFormatA to User32 interface
• Add WindowsNativePasteboardTest with 7 tests covering write, read, marker detection, and laziness verification

Design

Uses Windows delayed rendering: SetClipboardData(CF_HDROP, NULL) registers the format without providing data. When a consumer reads CF_HDROP, Windows sends WM_RENDERFORMAT to the clipboard owner window, which builds a DROPFILES structure with resolved file paths.

Key implementation details:

• Single-thread architecture: Hidden window + message loop on newSingleThreadContext (Windows requires clipboard owner and message pump on same thread)
• Cross-thread sync: CompletableDeferred for write results, PostMessage(WM_USER+1) to dispatch work to window thread
• Eager CrossPaste marker: Custom clipboard format set immediately to prevent self-consumption
• Correct GetMessage handling: Uses Function.getFunction("user32", "GetMessageW") with Int return to handle tri-state (>0/0/-1) properly, avoiding JNA's boolean mapping issue

Test plan

• writeFilesToClipboard returns valid sequence number for single file
• writeFilesToClipboard returns valid sequence number for multiple files
• writeFilesToClipboard returns -1 for zero count
• native clipboard single file is readable from JVM clipboard
• native clipboard multiple files are readable from JVM clipboard
• writeFilesToClipboard sets CrossPaste marker
• data provider is NOT called during write - only on read (laziness proof)

Tests are @EnabledOnOs(OS.WINDOWS) — run with ./gradlew app:desktopTest --tests "com.crosspaste.paste.WindowsNativePasteboardTest" on Windows.