rMLX 0.2.2

Multimodal release. Whisper transcription works end to end (decode correctness

• long-form) behind a new model-agnostic rmlx transcribe CLI; the dense
  Gemma 4 12B gemma4_unified any-to-any architecture is now supported for image
  and audio input; the standard Gemma 4 family gains native audio input through
  the serve path; and the unified vision color-fidelity bug is fixed. Plus
  release-signing and CI-hardening housekeeping. No breaking changes.

Added

• rmlx transcribe <audio> --model <snapshot> [--format vtt|srt|json|txt] —
  model-agnostic audio transcription CLI, arch-dispatched on config.json
  (Whisper today, a clean seam for future ASR). Decodes any container to 16 kHz
  mono internally (enabled symphonia isomp4+aac, so .m4a works). The HTTP
  endpoint and the CLI share one long-form engine. (#119)
• Gemma 4 12B unified (gemma4_unified) image + audio input. The dense
  any-to-any 12B has no SigLIP/Conformer tower — vision and audio are
  early-fusion via soft tokens projected straight into the shared 48-layer LM.
  Faithful encoder-free ports of Gemma4UnifiedVisionEmbedder (host patchify +
  3×3 merge → patch_ln1 → quantized patch_dense → factorized 2D pos-emb →
  embed_vision) and Gemma4UnifiedAudioFeatureExtractor (raw 16 kHz waveform
  → fixed 640-sample frames → embed_audio). Dispatched off is_unified_arch;
  the standard e4b/26b/31b SigLIP path is unchanged. (#120)
• Gemma 4 native audio input through the serve path. The Conformer
  audio_tower + embed_audio projector + USM feature extractor now load at
  startup alongside the vision tower, and input_audio parts are decoded → mel
  → AudioEncoder → soft tokens scattered at <|audio|>, mirroring the vision
  flow. Submitting audio to a model without an audio tower (or combining image +
  audio) returns a clear 503 — no silent drop. (#122)

Fixed

• Whisper transcription was empty / garbage. large-v3 has 100 language
  slots, shifting every special token +1 vs the v1/v2 layout the constants
  assumed — so TOK_TRANSCRIBE pointed at <|translate|> and the
  timestamp-begin hard-stop fired on <|notimestamps|>. Corrected the
  special-token layout and added the missing in-loop logit filters
  (SuppressBlank, SuppressTokens derived generally from the tokenizer, and a
  faithful ApplyTimestampRules). Long-form decode bounds are derived from
  n_text_ctx at runtime so the positional table can't overflow. Full 48-min
  real recording at temp 0 → normalized WER ≈ 0.079, deterministic. (#119)
• Gemma 4 12B unified vision color corruption. The encoder-free path read
  image soft tokens causally, but gemma4_unified conditions each image's
  soft tokens with bidirectional attention (the SigLIP path hides this by
  pre-integrating the image in its ViT). A per-prefill bidirectional overlay,
  keyed off the <start_of_image>/<end_of_image> markers and merged
  element-wise into each layer's causal/SWA mask, fixes color naming and layout;
  gated on has_image so text prefill is untouched. (LayerNorm eps also
  corrected to the PyTorch nn.LayerNorm default 1e-5.) A 100%-uniform
  achromatic fill still reads as one level — an inherent property of the
  encoder-free projection (patch_ln1 normalizes the absolute level away),
  documented in docs/MODELS.md. (#127)
• --probe-smoke false BrokenPunctLoop on instruction-tuned snapshots.
  The probe fed a bare (no-chat-template) instruction; chat models degenerate on
  such out-of-distribution input (the mlx-lm reference reproduces it
  identically) — a probe artifact, not a 4-bit dequant bug. The smoke seed is
  now rendered through the snapshot's chat_template.jinja when present, falling
  back to the bare seed for base models; each entry point keeps its own canonical
  BOS resolver (no hardcoded id). (#121)

Security

• Pin CI actions (actions/checkout, dtolnay/rust-toolchain,
  Swatinem/rust-cache) to commit SHAs, add keyless cosign release signing
  (make release-sign), and drop a stale RustSec advisory ignore. (#116)

Changed

• scripts/release/source_sha256.sh --write now also bumps the formula url
  version, not just the sha256 (previously left the formula pointing at the old
  tag's tarball). (#118)
• docs/RELEASING.md documents the formula url-bump and Dependabot
  migration-push gotchas. (#115)