rMLX 0.2.8

Qwen3.5-family model-loading correctness and a CI-gateable smoke probe. The
weight-quant loaders no longer corrupt mxfp8/mxfp4 scales, dense Qwen3.5 mxfp8
checkpoints now load via fact-driven dispatch (no longer hardwired to the PARO
path), and rmlx info --probe-smoke returns distinct exit codes so a load
failure can no longer masquerade as success. No breaking changes.

Added

• Dense Qwen3.5 mxfp8 loader + fact-driven dispatch. Both
  Qwen3_5ForConditionalGeneration and Qwen3_5MoeForConditionalGeneration
  now route by checkpoint facts, not the arch string: is_paroquant() selects
  the PARO vs the standard loader (the two share an arch string and differ only
  by quantization_config.quant_method), a shared resolve_prefix probes shard
  headers for the tensor prefix, and the MLP block is chosen per layer by tensor
  presence (dense SwiGLU vs sparse MoE). A defensive guard hard-errors if a PARO
  checkpoint ships MoE expert tensors. Dense Qwen3.5 mxfp8 snapshots now serve
  end-to-end. (#191, closes #189)

Fixed

• mxfp8/mxfp4 uint8 E8M0 scales corrupted at load → MoE prefill crash. The
  Qwen3.5-MoE and Qwen3 loaders blanket-cast every quantized .scales tensor to
  bf16, which is correct for affine (float) scales but corrupts mxfp's uint8 E8M0
  scales, crashing the first prefill with dequantize: Scale type must be uint8.
  A new per-tensor bf16_scales gate casts only float scales and passes uint8
  scales through verbatim. (#190, closes #188)

Changed

• rmlx info --probe-smoke now returns distinct exit codes for CI gating.
  Previously every non-Broken* outcome — including a supported-arch load
  failure and an inconclusive zero-token run — exited 0, so a loader regression
  read as a pass. Exit codes are now 0 ok, 1 broken, 3 load-fail, 4
  inconclusive, 5 unsupported (2 is reserved for clap arg-parse errors).
  healthcheck marks load-fail / inconclusive / broken as Red and unsupported
  as a non-fatal skip. (#193, closes #192)
• Bumped anyhow 1.0.102 → 1.0.103 (fixes a Stacked-Borrows UB in
  Error::downcast_mut) and uuid 1.23.3 → 1.23.4. (#187)