Hand and Zoom cursors drawn like the tool cursors (Windows showed the move arrows, no magnifier)

[zakariayacine]

What and why

On Windows the Hand tool, Space and the Zoom tool showed the wrong cursors: winit maps egui's Grab and
Grabbing to the four-headed move cursor (IDC_SIZEALL, winit/src/platform_impl/windows/util.rs) and has
nothing for ZoomIn/ZoomOut, so holding Space showed arrows instead of a hand, and the Zoom tool (Z) showed no
magnifier. Those four were the only tool cursors left to the system (cursors.rs drew every other tool).

They are now vector glyphs like the others, in the same visual grammar (black on a white halo, Illustrator's
grammar): an open hand with the thumb to the left (Hand tool, Space), the same hand closed while the view is
dragged, and a magnifier with a plus in the lens or a minus with Alt. Shown as OS cursors on the desktop (#444) and
painted on the web as the other glyphs are. The canvas routes the Space, Hand and Zoom states through the same path
as the tool cursors instead of asking egui for system cursors.

How it was tested

• cursors::tests: the four glyphs rasterize at every scale with the other 34, inside the 50 px limit, with an
  opaque body and the hotspot inside the bitmap; only the busy state (NotAllowed) stays a system cursor.
• canvas::tests pass unchanged (54 tests in cursors:: and canvas::).
• Seen on Windows 11 in a release build: Space shows the hand, dragging the closed hand, Z the magnifier, Alt the
  minus.
• cargo xtask ci: all 7 steps passed (fmt, clippy, test, assets, brands, layers, wasm).

Developed with AI assistance (Claude Code); reviewed and tested locally on Windows 11.

Checklist

• cargo xtask ci passes.
• No panics in shipped code.
• Clean-room: original glyphs drawn in code; nothing copied from Adobe products or GPL/AGPL code.
• No new assets (the glyphs are code, like the other cursors).

🤖 Generated with Claude Code

[bflatastic]

Thanks @zakariayacine, merged! Windows finally gets a real hand and magnifier.

I added one commit on top. When I rendered the glyphs, the fingers' halos covered each other's outlines, and the plus in the magnifier had a gap where its bars crossed. Now every halo is drawn before any outline, and the plus and minus are drawn without halos, since the lens is already white. Rebased onto main, and the full local gate passed.