Add imatrix headQ6 variant (NEO-style imatrix + Q6_K output head)

Add imatrix base variant (NEO-style general+code imatrix; measured -10% median KL, +0.8pp top-token vs non-imatrix)

Add f16-MTP-head variant (BF16 27B donor head kept at f16; draft acceptance rate = 0.76852)

Add Q6-head variant

Add base variant (ROCmFP4 STRIX + Q8 emb; transplanted MTP head)

initial commit