Replace the single legacy formula (2 * n_kv_heads * head_dim * n_layers
* n_ctx * bpe) with 5-path estimation that reads 8 additional GGUF
metadata fields:
1. MLA (DeepSeek-V2/V3, GLM-4.7, GLM-5, Kimi-K2.5) -- K-only cache
using compressed KV latent + RoPE; no separate V allocation
2. Hybrid Mamba (Qwen3.5-27B, Qwen3.5-35B-A3B) -- only attention
layers (1 in N) carry KV; Mamba layers have none
3. Sliding Window (Gemma-3, gpt-oss) -- SWA layers cache
min(ctx, window) tokens instead of the full context
4. Standard GQA -- uses explicit key_length/value_length from GGUF
instead of embed // n_heads (which is wrong for many models)
5. Legacy fallback -- identical to old formula for old GGUFs
New GGUF fields parsed: attention.key_length, attention.value_length,
attention.sliding_window, full_attention_interval,
attention.kv_lora_rank, attention.key_length_mla, ssm.inner_size,
ssm.state_size.
Validated against 9 real GGUF files (72/72 field checks pass).
The legacy formula was off by +682% for Gemma-3 and -81% for
DeepSeek-V3.1.