Add Hugging Face Hub as a source

The Hugging Face Hub API is public and keyless, exposing downloads and likes per model/dataset plus lastModified. For AI-flavored topics (a large share of expected queries), 'which models/datasets shipped or moved this month' is strong recency signal.

Add `scripts/huggingface.ts`: search models + datasets by topic, filter to the window, include downloads/likes in the context. Consider only invoking when the topic looks AI-related, or always running it and letting thin results speak for themselves.

Constraint check: official public API, keyless. ✅

Start with the Hugging Face Hub API documentation and define scripts/huggingface.ts around topic searches for models and datasets. Verify filtering by the requested time window and inclusion of downloads, likes, and lastModified in the context; done means the source works without an API key and its invocation behavior is resolved.

Written by the indexing model from the issue text.