Fix the bugs the type errors exposed (RnetSession.send body, HLS proxy session, title cache fallback, mux progress) and gate mypy in pre-commit, warn-only in CI.
Fix DASH SegmentTimeline negative @r and Pattern, TTML sidecar sets with no contentType, HLS CHANNELS identifiers and Dolby channel masks; test against 408 public DASH/HLS/ISM manifests.
- Create `unshackle/core/providers/` package with abstract base class, IMDBApi (free, no key), SIMKL, and TMDB provider implementations
- Add consensus-based ID enrichment: cross-references IMDB IDs with TMDB and SIMKL, drops all data from providers that disagree on tmdb_id (likely resolved to wrong title)
- Cache enriched IDs alongside raw provider data so they survive cache round-trips
- Genericize TitleCacher with `cache_provider()`/`get_cached_provider()` replacing provider-specific methods; respect `--no-cache` flag
- Add `--imdb` CLI flag to dl command for direct IMDB ID lookup