supertonic: fused Metal kernels + layout-flexible activations

[ogad-tether]

Summary

Lands the Supertonic 2 custom op family onto qvac-ext-ggml@speech so the
tts-cpp Supertonic Metal path
can consume them via the upstream ggml-speech vcpkg port without
carrying a local overlay-port patch in qvac-ext-lib-whisper.cpp.

What's added

Five fused Metal kernels (each with a CPU forward as the parity backstop)
collapse multi-op sub-graphs that the Supertonic graph builders emit per
ConvNeXt / attention block. Every kernel uses a stride-parameterised
body so the same compiled kernel handles both [T, C] and [C, T]
activations via a layout flag in op_params:

Op	Replaces
SUPERTONIC_DEPTHWISE_1D	edge-clamp/causal pad + im2col + mul_mat + add (K ∈ {3, 5, 7}; symmetric or causal-left padding)
SUPERTONIC_LAYER_NORM_CHANNEL	permute + cont + norm + mul + add + permute + cont
SUPERTONIC_PW2_RESIDUAL	add(bias) + mul(gamma) + add(residual)
SUPERTONIC_BIAS_GELU	add(bias) + gelu_erf
SUPERTONIC_EDGE_PAD_1D	edge-replicate causal/symmetric pad

Public ctors in include/ggml.h:

• ggml_supertonic_depthwise_1d{,_ct,_causal_ct} — [T,C] symmetric / [C,T] symmetric / [C,T] causal
• ggml_supertonic_layer_norm_channel{,_ct}
• ggml_supertonic_pw2_residual{,_ct}
• ggml_supertonic_bias_gelu{,_ct}
• ggml_supertonic_edge_pad_1d{,_ct}

GGML_OP_COUNT bumps 96 → 101.

Provenance

Authored against ggml-org/ggml master commit a8db410a, rebased onto
qvac-ext-ggml@speech HEAD 91676f0. Patches applied cleanly modulo
a few additive-only context shifts (no semantic conflicts).

Test plan

End-to-end verification on Apple M2:

• Build qvac-ext-ggml feat/supertonic-ops via vcpkg with Metal feature ON
• Build qvac-ext-lib-whisper.cpp PR #15 tts-cpp against this branch (overlay-port redirected via vcpkg_from_git file://)
• Synthesize through supertonic-cli — writes valid 2.6 s WAV at 44.1 kHz
• Run supertonic-bench — vocoder 14 ms / vec_est 71 ms / total 108 ms median (all _ct paths engaged including the causal depthwise on the 10-block vocoder ConvNeXt chain)
• Reviewer to confirm no regression on non-Supertonic ggml consumers (all additions are net-new; no existing code paths modified)

Downstream

Once this lands on speech, qvac-ext-lib-whisper.cpp PR #15's
overlay-port can be deleted entirely and tts-cpp consumes patched ggml
directly from the ggml-speech vcpkg port.

🤖 Generated with Claude Code

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