Double-clicking a workbook, Open With, dropping on the Dock icon and
`open -a GridCraft book.xlsx` send the app a kAEOpenDocuments Apple event
instead of command-line paths. winit 0.30 doesn't handle it, so AppKit
answered "GridCraft cannot open files in the Excel Workbook format".
Register the handler with the audited fmv-macos-events crate that PdfCraft
and PhotoCraft already use: it does the Objective-C interop (unsafe, which
this workspace forbids) behind a safe main-thread API and leaves winit's
delegate alone. Opened paths go through SheetApp::open_path; a quit event
closes the window. The registration lives in main() until the event loop
returns, so the event that launched the app is caught too.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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