Fix GPU encoding black frames and improve debug logging

- Add CUDA sync before encoding to ensure RGB->NV12 kernel completes
- Add debug logging for frame data validation (sum check)
- Handle GPUFrame objects in GPUHLSOutput.write()
- Fix cv2.resize for CuPy arrays (use cupyx.scipy.ndimage.zoom)
- Fix fused pipeline parameter ordering (geometric first, color second)
- Add raindrop-style ripple with random position/freq/decay/amp
- Generate final VOD playlist with #EXT-X-ENDLIST

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/templates/runs/detail.html

@@ -103,15 +103,34 @@
         const video = document.getElementById('live-video');
         const statusEl = document.getElementById('stream-status');
         const loadingEl = document.getElementById('stream-loading');
-        const hlsUrl = '/runs/{{ run.run_id }}/hls/stream.m3u8';
+        // Use dynamic playlist endpoint with cache busting
+        const baseUrl = '/runs/{{ run.run_id }}/playlist.m3u8';
+        function getHlsUrl() {
+            return baseUrl + '?_t=' + Date.now();
+        }
         let hls = null;
         let retryCount = 0;
         const maxRetries = 120;  // Try for up to 4 minutes
         let segmentsLoaded = 0;
 
+        // Custom playlist loader that adds cache-busting to every request
+        class CacheBustingPlaylistLoader extends Hls.DefaultConfig.loader {
+            load(context, config, callbacks) {
+                if (context.type === 'manifest' || context.type === 'level') {
+                    const url = new URL(context.url, window.location.origin);
+                    url.searchParams.set('_t', Date.now());
+                    context.url = url.toString();
+                }
+                super.load(context, config, callbacks);
+            }
+        }
+
         function initHls() {
             if (Hls.isSupported()) {
                 hls = new Hls({
+                    // Custom loader to bust cache on playlist requests
+                    pLoader: CacheBustingPlaylistLoader,
+
                     // Stay far behind live edge - rendering is slow (~0.1x speed)
                     // 10 segments = 40s of buffer before catching up
                     liveSyncDurationCount: 10,       // Stay 10 segments behind live edge
@@ -177,7 +196,7 @@
                                     // Exponential backoff with jitter
                                     const delay = Math.min(1000 * Math.pow(1.5, Math.min(retryCount, 6)), 10000);
                                     setTimeout(() => {
-                                        hls.loadSource(hlsUrl);
+                                        hls.loadSource(getHlsUrl());
                                     }, delay + Math.random() * 1000);
                                 } else {
                                     statusEl.textContent = 'Stream unavailable';
@@ -246,11 +265,11 @@
                     }
                 }, 1000);
 
-                hls.loadSource(hlsUrl);
+                hls.loadSource(getHlsUrl());
                 hls.attachMedia(video);
             } else if (video.canPlayType('application/vnd.apple.mpegurl')) {
                 // Native HLS support (Safari)
-                video.src = hlsUrl;
+                video.src = getHlsUrl();
                 video.addEventListener('loadedmetadata', function() {
                     loadingEl.classList.add('hidden');
                     statusEl.textContent = 'Playing';