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/routers/runs.py

@@ -1137,6 +1137,52 @@ async def serve_hls_content(
     raise HTTPException(404, f"File not found: {filename}")
 
 
+@router.get("/{run_id}/playlist.m3u8")
+async def get_playlist(run_id: str, request: Request):
+    """Get live HLS playlist for a streaming run.
+
+    Returns the latest playlist content directly, allowing HLS players
+    to poll this URL for updates without dealing with changing IPFS CIDs.
+    """
+    import database
+    import os
+    import httpx
+    from fastapi.responses import Response
+
+    await database.init_db()
+
+    pending = await database.get_pending_run(run_id)
+    if not pending:
+        raise HTTPException(404, "Run not found")
+
+    ipfs_playlist_cid = pending.get("ipfs_playlist_cid")
+    if not ipfs_playlist_cid:
+        raise HTTPException(404, "Playlist not yet available")
+
+    # Fetch playlist from local IPFS node
+    ipfs_api = os.environ.get("IPFS_API_URL", "http://celery_ipfs:5001")
+
+    try:
+        async with httpx.AsyncClient(timeout=10.0) as client:
+            resp = await client.post(f"{ipfs_api}/api/v0/cat?arg={ipfs_playlist_cid}")
+            if resp.status_code != 200:
+                raise HTTPException(502, "Failed to fetch playlist from IPFS")
+            playlist_content = resp.text
+    except httpx.RequestError as e:
+        raise HTTPException(502, f"IPFS error: {e}")
+
+    return Response(
+        content=playlist_content,
+        media_type="application/vnd.apple.mpegurl",
+        headers={
+            "Cache-Control": "no-cache, no-store, must-revalidate",
+            "Pragma": "no-cache",
+            "Expires": "0",
+            "Access-Control-Allow-Origin": "*",
+        }
+    )
+
+
 @router.get("/{run_id}/ipfs-stream")
 async def get_ipfs_stream_info(run_id: str, request: Request):
     """Get IPFS streaming info for a run.