vulkan: add TQ2_0 (ternary) support (llama/25850)

vulkan: add TQ2_0 (ternary) support (llama/25850)

* vulkan: TQ2_0 (ternary) support — dequant + dedicated mul_mat_vec + matmul via dequant_funcs

First Vulkan ternary type in ggml. Correctness: OM-125m TQ2_0 vs F16 top-12
logprobs identical to 4 decimals fully offloaded (float dequant path, no Q8_K
activation quant). Speed at 125m ~= F16 (overhead-bound at this scale); the
bandwidth win targets larger BitNet SKUs. MMQ/int-dot path intentionally not
wired yet.

Co-Authored-By: Claude Fable 5 <redacted>
* tests: enable TQ2_0 in backend-ops type lists

Vulkan now implements TQ2_0 (dequant, mul_mat_vec, mul_mm, get_rows); backends
without support skip via not-supported as usual. TQ1_0 stays disabled.

Co-Authored-By: Claude Fable 5 <redacted>
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Co-authored-by: Michael Trabalka <redacted>
Co-authored-by: Claude Fable 5 <redacted>