Add Drawing and GPU sample pages to Blazor demo

[Copilot]

Brings in the sample-only changes from mono/SkiaSharp#3528 into the SkiaSharp.Extended Blazor demo app.

New pages

• Drawing.razor — Interactive stroke-recording canvas: pointer down/move/up for drawing, mouse wheel to resize brush, color picker toolbar, clear button. Uses @onpointerdown/@onpointermove/@onpointerup/@onwheel (adapted from PR's Touch/EnableTouchEvents API which isn't released yet).
• GPU.razor — Real-time SkSL metaball lava lamp via SKGLView + EnableRenderLoop + SKRuntimeEffect.BuildShader(). 6 blobs orbit on Lissajous curves; pointer drag adds a white-hot blob via uniforms. FPS counter throttled to ~4 Hz Blazor updates.

Nav / layout

• NavMenu.razor — Added "SKIA" section with GPU and Drawing links + Bootstrap SVG icons (NavMenu.razor.css)
• MainLayout.razor.css — height: 100vh + overflow: hidden + flex column min-height: 0 on main for full-viewport canvas pages

Package

• SkiaSharp.Views.Blazor bumped 3.119.1 → 3.119.2

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• https://api.github.com/repos/mono/SkiaSharp/pulls/3528/files
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (http block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

Please look at mono/SkiaSharp#3528 and bring in the sample changes only. We want the new sample but none of the other things.

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