fix: guard video.play() for jsdom and fix Hls mock case mismatch

- Defensive null check on video.play() return value (jsdom returns undefined)
- Fix test mock: win.Hls (not win.HLS) to match viewer.js window.Hls reference
- All 39/39 tests now pass

src/viewer/viewer.js

@@ -37,7 +37,8 @@ function playHls(video, manifestUrl, panel) {
   if (!window.Hls || !window.Hls.isSupported()) {
     console.log('[goon-viewer] Native HLS support detected, using direct source');
     video.src = manifestUrl;
-    video.play().catch(() => { /* autoplay blocked — user interaction required */ });
+    const p = video.play();
+    if (p) p.catch(() => { /* autoplay blocked — user interaction required */ });
     return;
   }
 
@@ -55,7 +56,8 @@ function playHls(video, manifestUrl, panel) {
 
   hls.on(window.Hls.Events.MANIFEST_PARSED, () => {
     console.log('[goon-viewer] HLS manifest parsed, playing');
-    video.play().catch(() => { /* autoplay blocked */ });
+    const p = video.play();
+    if (p) p.catch(() => { /* autoplay blocked */ });
   });
 
   hls.on(window.Hls.Events.LEVEL_SWITCHED, () => {