feat: hardware detection, cf-docuvision service, documents ingestion pipeline
Closes #5, #7, #8, #13
## hardware module (closes #5)
- HardwareSpec, LLMBackendConfig, LLMConfig dataclasses
- VramTier ladder (CPU / 2 / 4 / 6 / 8 / 16 / 24 GB) with select_tier()
- generate_profile() maps HardwareSpec → LLMConfig for llm.yaml generation
- detect_hardware() with nvidia-smi / rocm-smi / system_profiler / cpu fallback
- 31 tests across tiers, generator, and detect
## cf-docuvision service (closes #8)
- FastAPI service wrapping ByteDance/Dolphin-v2 (Qwen2.5-VL backbone)
- POST /extract: image_b64 or image_path + hint → ExtractResponse
- Lazy model loading; JSON-structured output with plain-text fallback
- ProcessSpec managed blocks added to all four GPU profiles (6/8/16/24 GB)
- 14 tests
## documents module (closes #7)
- StructuredDocument, Element, ParsedTable dataclasses (frozen, composable)
- DocuvisionClient: thin HTTP client for cf-docuvision POST /extract
- ingest(): primary cf-docuvision path → LLMRouter vision fallback → empty doc
- CF_DOCUVISION_URL env var for URL override
- 22 tests
## coordinator probe loop (closes #13)
- _run_instance_probe_loop: starting → running on 200; starting → stopped on timeout
- 4 async tests with CancelledError-based tick control
pyr0ball
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