fix(viewer): apply NVIDIA and WebKitGTK workarounds before creating the webview (#226)

* fix(viewer): apply NVIDIA and WebKitGTK workarounds before creating the webview

On Linux the Tauri viewer is WebKitGTK, and on NVIDIA hosts it failed in
three ways: the Wayland window died at once with "Error 71 (Protocol
error)", the X11 window painted solid grey, and the pthread WASM build
could not bootstrap because JavaScriptCore hides SharedArrayBuffer.

A new linux_graphics module runs in the internal viewer process before
tauri::Builder, so the WebKit processes inherit the environment. It sets,
only when the variable is unset:

- JSC_useSharedArrayBuffer=1 always
- __NV_DISABLE_EXPLICIT_SYNC=1 when the NVIDIA kernel driver is loaded,
  which keeps the fast DMA-BUF path working on Wayland (Tauri's
  documented fix)
- WEBKIT_DISABLE_DMABUF_RENDERER=1 when NVIDIA and the X11 backend,
  where DMA-BUF import fails and only the shared-memory path paints

The decision is a pure function with unit tests. Verified on NixOS with
WebKitGTK 2.52.6, driver 595.71.05, KDE Wayland: with no manual
environment the Wayland window now stays up and the X11 window renders
the sketch.

Refs the fastled-wasm Linux graphics guidance at
https://v2.tauri.app/develop/debug/linux-graphics/

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01M9rUkvoW2gVKYurtQJpi4i

* build: move zccache-fingerprint to 1.13.22 and the toolchain to Rust 1.95.0

The pinned zccache commit pulled in tikv-jemalloc-sys, whose configure
step fails under the zccache C wrapper ("cannot determine return type
of strerror_r"), so tests and clippy could not build on this host. The
current zccache release no longer depends on jemalloc; it requires
rustc 1.95.0, so rust-toolchain.toml moves from 1.94.1 to 1.95.0.

Verified locally on 1.95.0: the linux_graphics unit tests, workspace
clippy with -D warnings, the format check, and a release build.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01M9rUkvoW2gVKYurtQJpi4i

---------

Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

Author: zackees

Cargo.lock

@@ -40,7 +40,7 @@ tauri = { version = "2", features = ["devtools"] }
 tauri-build = { version = "2", features = [] }
 windows-sys = "0.61"
 # Parallel content-authoritative walker/hasher; remains compatible with Rust 1.85.
-zccache-fingerprint = { git = "https://github.com/zackees/zccache", rev = "1bd5b6387eff54695e37adbfacbb977079d6f174" }
+zccache-fingerprint = { git = "https://github.com/zackees/zccache", rev = "a7c84de53105ce41b2060bd9dd7730ef226e78a1" }
 shell-words = "1"
 globset = "0.4"
 tree-sitter = "0.26.9"

Cargo.toml

@@ -20,6 +20,8 @@ pub mod frontend;
 pub mod install;
 mod install_unlock;
 mod keyboard;
+#[cfg(target_os = "linux")]
+pub mod linux_graphics;
 pub mod path;
 mod paths_util;
 pub mod project;