feat: Add L2-L5 CPU kernels (WHT, FWHT/ACDC, Tropical, HRR) with dispatch integration

[peder1981]

Add L2–L5 algebraic kernels for CPU-only 1.58-bit inference

This PR adds four new algebraic kernels for the CPU-only inference path:

Level	Algebra	Kernel	Saves
L2	Walsh–Hadamard (no multiplications)	ggml-bitnet-wht	Replaces 256 maddubs with adds/subs in vec_dot
L3	ACDC (FWHT + diagonal)	ggml-bitnet-fwht	O(n log n) GEMV; needs ACDC-diagonalizable W
L4	Tropical (max, +)	ggml-bitnet-tropical	O(n·d + K·d) attention via top-K softmax over keys
L5	Holographic Reduced Repr. (FFT)	ggml-bitnet-hrr	d-dim vector stores N ≪ d "memories"

Files

• src/ggml-bitnet-{wht,fwht,tropical,hrr,common,dispatch,kv-cache,rag}.cpp — kernel implementations
• include/ggml-bitnet-{wht,fwht,tropical,hrr,common,dispatch,kv-cache,rag}.h — headers
• CMakeLists.txt, src/CMakeLists.txt, src/ggml-bitnet-mad.cpp — build integration
• patches/llama.cpp/ (5 patches) + scripts/apply-dispatch-patches.sh — Llama dispatch
• .gitmodules — ignore = dirty for local patch workflow

Design

• All kernels are opt-in via env vars (default = untouched I2_S GEMV)
• No GPU, no telemetry, no cloud calls
• Submodule pinned to 1f86f05 (same as upstream)

Part of a split from original PR #567. This is the core code portion.