Three categories of missed renames in CKPT_KEY_SUBST:
1. Shared experts: .shared_experts.gate_proj.→.ffn.shared_experts.w1. fired
but break prevented .mlp.→.ffn. from also applying, producing
mlp.ffn.shared_experts.w1. (double prefix). Fixed by including .mlp.
in the pattern. Added missing .shared_experts.down_proj. rule.
2. Indexer (layers 2+): .self_attn.compressor.indexer.* was caught by the
generic .self_attn.compressor.→.attn.mla_attn.compressor. rule, producing
wrong path attn.mla_attn.compressor.indexer.* instead of attn.indexer.*.
Added indexer-specific patterns (q_b_proj→wq_b, kv_norm→k_norm,
position_bias→compressor.ape, gate_proj→compressor.wgate,
kv_proj→compressor.wkv) before the generic compressor rule.
3. Compressor kv_proj/gate_proj: old .compressor.kv_proj.→.compressor.wkv.
pattern could never fire because .self_attn.compressor. matched first
(break). Merged into combined patterns that handle both the
self_attn.compressor→attn.mla_attn.compressor path AND the projection
rename in one step.
Checkpoint keys are model.layers.N.shared_experts.gate_proj.weight
but model params are layers.N.ffn.shared_experts.gate_up_proj.weight.
The .ffn. was missing from the rename, so stacked gate_up_proj
never matched params_dict.
The stacking logic skipped any key containing '.experts.' to avoid
MoE routed expert weights. But 'shared_experts' also matches that
substring, so gate_proj and up_proj were never stacked into
gate_up_proj. Changed to '.ffn.experts.' which only matches the
routed experts path.
Also includes POST-LOAD all-zero param scan.
