[jcgruesome]

Closes MKT-762

What

Installable screensaver for macOS (.saver, arm64) and Windows (.scr). Each run uses a synthetic graph, ReshapeX-family palette, fictional SKUs and queries, re-rolled every 60 s, with the ReshapeX logo. No real customer data ships.

• @kg/runtime bare-specifier seam: the screensaver Vite build swaps the data layer, so real queries/i18n never enter the bundle (checked by pnpm verify:screensaver, with a negative control).
• Synthetic kit generator with a denylist test (200 seeds), palette clamped to ReshapeX hues.
• macOS host: Swift ScreenSaverView + WKWebView, built with swiftc (no Xcode). Verified on hardware by the owner.
• Windows host: .NET WebView2, built by CI only. Untested on Windows (MKT-763).
• ?maxpx pixel budget (web default unchanged).

Not in this PR

Signing/notarization and the prospect download page (MKT-764). Minors from final review (MKT-765).

Learnings

• Vite resolve.alias matches import text, not resolved paths: relative imports like ./queries are not aliased. Use a bare specifier seam.
• Under macOS legacyScreenSaver, WebKit reports the page hidden and stops rAF after one frame. Fix: private _setWindowOcclusionDetectionEnabled: set to false (call the IMP; perform(_:with:) mishandles BOOL).
• ScreenSaverEngine ignores moduleDict on macOS 27, so the saver can only be selected by hand in System Settings.
• A multi-display view can be 7680x2160 pts; at 2x pixel ratio that ran at about 15 fps. Cap canvas pixels (4M).
• document.fonts.load resolves with an empty array when the face is missing; assert length > 0.
• A .scr is one file in System32: embed the web build and extract to %LOCALAPPDATA%; WebView2 user-data folder must not be next to the exe.

https://claude.ai/code/session_01UrC5iwLW3LmG3bkgWzHckb