v0.9.12

Cleaner error responses for bad queries

The portal now returns proper 400 Bad Request errors for query parameters that previously produced empty streams or were misclassified as server errors.

• Zero buffer_size and max_chunks rejected. Queries with these set to 0 now return 400 Bad Request instead of silently producing empty streams. (#105)
• Oversized worker responses surface as a client error. When a worker response exceeds the size limit, the portal returns 400 Bad Request instead of treating it as a server-side failure.

Full Changelog: v0.9.11...v0.9.12