This change introduces a complete Local Metadata Builder feature in the resolver
options panel. It allows users to scan local model files, create or update
.metadata.json sidecars, fill missing SHA256 hashes from safetensors headers or
file hashing, and review run history with cancel/error handling.
Changes include:
- backend API: /model_resolver/metadata-build/{capabilities,start,progress/{id},cancel}
- backend worker: core/metadata_builder.py with parallel metadata generation
- frontend section: Local Metadata Builder tab in Options
- frontend polling UI: progress, worker breakdown, history table, status/notifications