Port llama.cpp's HuggingFace hub-cache subsystem (http.h, hf-cache.{h,cpp})
into whisper.cpp's shared common library and wire -hf/--hf-repo +
-hff/--hf-file into whisper-cli. Phase 1 is cache-only: whisper_hf_resolve_model
scans the on-disk HF hub cache (get_cached_files + finalize_file) and maps
org/repo (+ optional file) to a concrete snapshot path, so a model already
pulled by the hf CLI resolves with no -m path. An explicit -m still wins and
the no-args default stays models/ggml-base.en.bin.
The network download path is compiled but unused this phase (enabled in
Phase 2). Adds tests/test-hf-resolve.sh covering cache hit, missing-file
error (exit 3), -m regression, and the default path.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>