feat(sentry): tag events with the WebView engine and version (#4952)

Forwarded browser events carry os/rust/device context but no browser context,
so crashes couldn't be correlated with the WebView version. The app now reports
its User-Agent at startup via a set_webview_info command; the parsed engine
(Chromium/WebKit) and major version are stored and attached as webview.engine
and webview.version tags in before_send, covering both Rust panics and
forwarded browser events.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/readest-app/src/services/nativeAppService.ts

@@ -595,6 +595,13 @@ export class NativeAppService extends BaseAppService {
   override async init() {
     const execDir = await invoke<string>('get_executable_dir');
     this.execDir = execDir;
+    // Report the WebView User-Agent so Sentry can tag crashes with the
+    // engine/version (the injected browser SDK's UA context isn't forwarded).
+    try {
+      await invoke('set_webview_info', { userAgent: navigator.userAgent });
+    } catch (err) {
+      console.warn('[nativeAppService] set_webview_info failed:', err);
+    }
     // Ask Rust whether the in-app updater must stay hidden (READEST_DISABLE_UPDATER,
     // Flatpak, or a Linux deb/rpm/pacman install that Tauri can't self-update). The
     // command is the reliable source of truth; the `__READEST_UPDATER_DISABLED`