Move tauri imports behind platform abstraction, merge CUDA build into release workflow

- Add openPath and pickDirectory to PlatformFilesystem interface
- Remove direct @tauri-apps/plugin-shell and plugin-dialog imports from app
- Merge build-cuda.yml into release.yml as a parallel job

tauri/src/platform/filesystem.ts

@@ -1,4 +1,4 @@
-import type { PlatformFilesystem, FileFilter } from '@/platform/types';
+import type { FileFilter, PlatformFilesystem } from '@/platform/types';
 
 export const tauriFilesystem: PlatformFilesystem = {
   async saveFile(filename: string, blob: Blob, filters?: FileFilter[]) {
@@ -12,9 +12,8 @@ export const tauriFilesystem: PlatformFilesystem = {
 
     if (!filePath) return; // User cancelled the dialog
 
-    const resolvedPath = typeof filePath === 'string'
-      ? filePath
-      : (filePath as { path: string }).path;
+    const resolvedPath =
+      typeof filePath === 'string' ? filePath : (filePath as { path: string }).path;
 
     if (!resolvedPath) {
       throw new Error('Failed to resolve save path from dialog');
@@ -23,4 +22,17 @@ export const tauriFilesystem: PlatformFilesystem = {
     const arrayBuffer = await blob.arrayBuffer();
     await writeFile(resolvedPath, new Uint8Array(arrayBuffer));
   },
+
+  async openPath(path: string) {
+    const { open } = await import('@tauri-apps/plugin-shell');
+    await open(path);
+  },
+
+  async pickDirectory(title: string) {
+    const { open } = await import('@tauri-apps/plugin-dialog');
+    const selected = await open({ directory: true, title });
+    if (!selected) return null;
+    const dir = typeof selected === 'string' ? selected : (selected as { path: string }).path;
+    return dir || null;
+  },
 };