Per Copilot's review: Ctrl+Y → delete-line and Ctrl+Shift+/ → block-
comment under monaco's CtrlCmd modifier translate to Cmd+Y / Cmd+Shift+/
on macOS, which don't match the actual macOS JetBrains keymap (delete
line is Cmd+Backspace, block-comment is Option+Cmd+/, and Cmd+Y in Mac
IntelliJ is "Show Quick Definition").
Pick the right binding per platform. CE has no existing macOS detection
helper — there are scattered ad-hoc navigator.userAgent checks but no
central spot — so add a small `isMacintosh` constant in static/utils.ts
that mirrors monaco's own platform.js detection. Cheap to reuse next
time we need it; better than another inline ad-hoc check.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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