Fix mobile share sheet not opening on download tap

Two iOS Safari issues prevented the share sheet from appearing:
- canShare() was probed with an empty placeholder File, which reports
  false on iOS, so the share path was skipped and it silently fell back
  to a hidden download. Now test canShare against the real fetched file.
- The /versions fetch before the file fetch consumed the user activation
  iOS requires for navigator.share(). On mobile, skip the version menu
  and share the primary file directly within the tap gesture.

Author: willuhmjs

src/lib/components/download/DownloadVersionPicker.svelte

@@ -54,19 +54,20 @@
 
 	async function triggerDownload(id: string) {
 		// On mobile, open the native share sheet so users can "Save to Photos"
-		// instead of dumping the file into Files/Downloads. Falls back to a plain
-		// download on desktop or when the Share API is unavailable.
-		const canShareFiles =
-			isMobileDevice() && navigator.canShare?.({ files: [new File([], 'test')] });
-		if (canShareFiles) {
+		// instead of dumping the file into Files/Downloads. canShare must be tested
+		// against the *real* file — an empty placeholder File reports false on iOS
+		// Safari, which would silently skip the share sheet.
+		if (isMobileDevice()) {
 			try {
 				const res = await fetch(fileUrl(id));
 				if (!res.ok) throw new Error('fetch failed');
 				const blob = await res.blob();
 				const name = filenameFromResponse(res) || 'download';
 				const file = new File([blob], name, { type: blob.type });
-				await navigator.share({ files: [file] });
-				return;
+				if (navigator.canShare?.({ files: [file] })) {
+					await navigator.share({ files: [file] });
+					return;
+				}
 			} catch (e: any) {
 				if (e.name === 'AbortError') return; // user dismissed the share sheet
 				console.warn('Share unavailable, falling back to download:', e);
@@ -112,6 +113,13 @@
 			open = false;
 			return;
 		}
+		// On mobile, share the primary file directly within this tap gesture.
+		// Fetching the versions list first would consume the user activation that
+		// iOS requires for navigator.share(), so we skip the version menu there.
+		if (isMobileDevice()) {
+			triggerDownload(downloadId);
+			return;
+		}
 		open = true;
 		loaded = false;
 		loadVersions();