Add Global Video Metadata Support

Video metadata - title, author, description, tags - is the invisible backbone of professional workflows. Right now, embedding this info cleanly into JSON outputs is a blind spot: despite platforms like YouTube demanding rich metadata, most systems pass files bare-bones. The new schema adds a metadata object to JSON output, letting creators embed title, author, and custom tags seamlessly. For example, a documentary’s JSON now includes "title": "Voices of the Midwest", "author": "Maya Chen", "tags": ["documentary", "midwest", "2024"], so the file carries context from creation. This matters because metadata improves searchability, platform compatibility, and archival integrity. But here is the deal: when metadata is present, the engine maps each field directly - title via -metadata title, author via author, and tags via -metadata tags. Without it, rendering stays smooth and backward safe. Still, some misunderstand: metadata isn’t just decorative; it’s critical for analytics and rights management. Don’t skip validation - ensure title and description are strings, tags an array. Older files work blind to new fields. In a world where every frame tells a story, metadata tells the full one - are you giving your video the voice it deserves?