Scrawl Linux preview 2: CPU compatibility fix

Linux preview 2 fixes the CPU-instruction crash reported in #82. This is an early Linux build for Ubuntu 24.04 or newer, based on the Linux branch's 0.3.10 version. The filenames and --version still say 0.3.10.

The previous preview compiled ggml for the build machine's CPU. This build disables GGML_NATIVE, bundles separate x86 CPU backends selected at runtime, and uses a portable CPU backend on aarch64. Rust builds also have explicit portable CPU baselines. In particular, AVX-VNNI and AVX512-VNNI are treated as separate capabilities.

Download and run

Choose x86_64 for Intel/AMD or aarch64 for ARM64. For Intel/AMD:

chmod +x Scrawl-0.3.10-linux-x86_64.AppImage
./Scrawl-0.3.10-linux-x86_64.AppImage --appimage-extract-and-run app

Download SHA256SUMS beside the AppImage and verify it with:

sha256sum --check --ignore-missing SHA256SUMS

Tap Alt+Shift+S to start and finish recording. Hold Shift to draw. On Wayland, input monitoring still needs membership in the input group and a new login; see the first preview's setup instructions and desktop limitations.

Verification

• macOS, Windows and Linux builds and unit tests passed.
• Both AppImages, instruction audit and packaged inference passed. Both architectures ran the model on two seconds of audio using the libraries extracted from their AppImage.
• x86 repeated inference and generated a demo bundle under Intel SDE Ice Lake, with assertions that AVX512-VNNI is present and AVX-VNNI is absent. Confirmation on the reporter's Ryzen 8700G is still pending in #82.

PR #84 is merged into feat/linux. The tag points to 1846e055f4fc57f94c363a7432382a637fd1d9a6, whose source tree matches the tested commit 329c62b7e48ede23488bd738977a7e59607c6158. These are the exact tested CI artifacts. This prerelease does not update the stable site or Sparkle feed.