v0.1.8

v0.1.8 — full native GGUF quant coverage + f16 subnormal fix

Fixed
- cortiq-core f16_to_f32 halved every subnormal half-float (subnormal biased
  exponent was 127-15-e, should be 113-e). This corrupted GGUF K-quant
  super-block scales (frequently subnormal) → garbage output. Now correct,
  with round-trip tests.

Added
- import-gguf: native dequant for every common ggml type — Q4_0/1, Q5_0/1,
  Q8_0, Q2_K..Q6_K, Q8_K, BF16, IQ4_NL/XS (faithful ports of ggml
  dequantize_row_*). Q4_K/Q5_K/Q6_K unit-tested vs fp16 ground truth; all nine
  Qwen2.5 GGUF quantizations convert and generate coherently. IQ1/2/3 grid
  codebooks are refused with a clear error (no silent garbage).
- import-gguf accepts an HF repo id (best .gguf auto-picked + downloaded) or
  owner/repo/file.gguf; --hf-token. Linear-attention/SSM (GatedDeltaNet) GGUFs
  are refused with a pointer to the safetensors path.
- convert: native fused-GatedDeltaNet split (qwen3_next/AgentWorld
  in_proj_qkvz/ba group-interleaved → canonical hub tensors); pure row
  permutation, unit-tested. Not yet generation-verified on real fused weights.
- convert: actionable error for a GGUF-only repo instead of a raw config.json 404.