Summary
Encoding long videos can fail before upload begins because the encoded output is assembled into one contiguous in-memory buffer.
This results in allocation or byte-size errors for sufficiently large videos.

Steps to reproduce

1. Upload a video longer than approximately 16 minutes (remaining under the current 1 GB upload limit).
2. Start encoding.

Current behavior
Encoding fails with a memory allocation or byte-size error before upload starts.

Expected behavior
Encoded output should be streamed instead of buffered into a single large allocation so that longer videos can be processed successfully.

Technical notes

• The encoder currently assembles the final output using a single BufferTarget, resulting in one contiguous allocation.
• A streaming output implementation would significantly reduce peak memory usage.