fix: HttpRangeReader stall detection, CDN re-resolve, HF API resolve Root cause: 21 GB tensor reads stall silently when HuggingFace CDN drops the TCP connection. curl sits forever with no data. Fixes: - --speed-limit 100000 --speed-time 30: abort if < 100 KB/s for 30s - Re-resolve URL on 403 (CDN token expiry after ~1 hour) - Segment-aligned fetches (no overlapping reads on sequential access) - 6 retries (was 4) with capped exponential backoff (max 32s) - from_hf() constructor: resolves via huggingface_hub Python API first, falls back to curl HEAD, then HF REST API. Stores repo/filename for automatic re-resolution on token expiry. - resolve_hf_url() tries 3 methods: Python HF API → curl HEAD → REST API https://claude.ai/code/session_01HmdXNPit7QsTCfhJFef3Ee#74