Fix blank WebKit window in Wayland AppImage sessions

[Copilot]

AstrBot AppImage could open a blank window on KDE Plasma Wayland while WebKitWebProcess aborted with EGL_BAD_PARAMETER; the backend remained reachable on localhost.

• Linux AppImage fallback
  • Detect AppImage launches in Wayland sessions.
  • Set GTK’s backend to X11 before Tauri/WebKit initialization, avoiding the bundled Wayland/EGL path.
  • Preserve a user-provided GDK_BACKEND value.

if wayland_display.is_some() && appimage.is_some() && existing_gdk_backend.is_none() {
    std::env::set_var("GDK_BACKEND", "x11");
}

• Coverage
  • Add focused cases for Wayland AppImage fallback, non-AppImage launches, missing Wayland display, and explicit backend overrides.

• Fixes [Bug] ArchLinux下使用KDE Plasma Wayland环境下白屏 #174

Summary by Sourcery

Fix Linux AppImage WebKit startup failures on Wayland by selecting a compatible GTK backend before desktop initialization.

Bug Fixes:

• Prevent blank WebKit windows in Linux AppImage sessions running under Wayland by defaulting GTK to X11 when no backend override is provided.

Enhancements:

• Apply the workaround before Tauri initialization while preserving explicit GDK backend settings.

Tests:

• Add coverage for AppImage and AppDir detection, Wayland requirements, and explicit GDK backend overrides.

[sourcery-ai]

Hey - I've found 1 issue

Prompt for AI Agents

Please address the comments from this code review:

## Individual Comments

### Comment 1
<location path="src-tauri/src/app_runtime.rs" line_range="8-18" />
<code_context>

 #[cfg(target_os = "linux")]
 mod linux_webkit_workaround {
+    const APPIMAGE_ENV: &str = "APPIMAGE";
+    const GDK_BACKEND_ENV: &str = "GDK_BACKEND";
     const WEBKIT_DISABLE_DMABUF_RENDERER_ENV: &str = "WEBKIT_DISABLE_DMABUF_RENDERER";
     const WAYLAND_DISPLAY_ENV: &str = "WAYLAND_DISPLAY";

+    fn should_set_gdk_backend_env(
+        existing_value: Option<&std::ffi::OsStr>,
+        wayland_display: Option<&std::ffi::OsStr>,
+        appimage: Option<&std::ffi::OsStr>,
+    ) -> bool {
+        existing_value.is_none() && wayland_display.is_some() && appimage.is_some()
+    }
+
</code_context>
<issue_to_address>
**issue (broader_impact):** The fallback recognizes only the `APPIMAGE` marker, so an AppImage-style launch that exposes `APPDIR` without `APPIMAGE` does not set `GDK_BACKEND=x11` and can still enter the bundled Wayland/EGL path. This is inconsistent with `is_linux_appimage_runtime`, which already treats either `APPIMAGE` or `APPDIR` as an AppImage runtime.

**Triggers:** When the AppImage runtime provides `APPDIR` but not `APPIMAGE`.

**Suggested fix:** Detect `APPDIR` as an AppImage marker as well, or reuse the existing Linux AppImage runtime detection helper.
</issue_to_address>

Sourcery assessment

Approval pending. 1 finding to address first.

Blocking findings: src-tauri/src/app_runtime.rs:18

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[sourcery-ai]

Sourcery assessment

Approved.

[zouyonghe]

@sourcery-ai review

[sourcery-ai]

Hey - I've reviewed your changes and they look great!

Sourcery assessment

Approved.

---

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