feat: add skill-seekers video --setup for GPU auto-detection and dependency installation

Auto-detects NVIDIA (CUDA), AMD (ROCm), or CPU-only GPU and installs the
correct PyTorch variant + easyocr + all visual extraction dependencies.
Removes easyocr from video-full pip extras to avoid pulling ~2GB of wrong
CUDA packages on non-NVIDIA systems.

New files:
- video_setup.py (835 lines): GPU detection, PyTorch install, ROCm config,
  venv checks, system dep validation, module selection, verification
- test_video_setup.py (60 tests): Full coverage of detection, install, verify

Updated docs: CHANGELOG, AGENTS.md, CLAUDE.md, README.md, CLI_REFERENCE,
FAQ, TROUBLESHOOTING, installation guide, video dependency plan

All 2523 tests passing (15 skipped).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pyproject.toml

@@ -121,12 +121,13 @@ video = [
 ]
 
 # Video processing (full: + Whisper + visual extraction)
+# NOTE: easyocr removed — it pulls torch with the wrong GPU variant.
+# Use: skill-seekers video --setup  (auto-detects GPU, installs correct PyTorch + easyocr)
 video-full = [
     "yt-dlp>=2024.12.0",
     "youtube-transcript-api>=1.2.0",
     "faster-whisper>=1.0.0",
     "scenedetect[opencv]>=0.6.4",
-    "easyocr>=1.7.0",
     "opencv-python-headless>=4.9.0",
     "pytesseract>=0.3.13",
 ]