test: Add 16 C++ unit tests, Python cross-validation, and air-gapped boot test

[Peder Munksgaard (peder1981)]

Test suite for L2-L5 algebraic kernels

Adds 16 C++ unit tests, Python cross-validation scripts, and infrastructure:

Test	Subtests	Kernel	Property-based?
test_bitnet_common	5/5	shared	—
test_wht	5/5	L2	—
test_acdc	5/5	L3	—
test_acdc_properties	4/4 (1000 inputs each)	L3	✅
test_tropical	5/5	L4	—
test_sparse_attention	5/5	L4	—
test_l4_sparse_properties	3/3 (topK correctness)	L4	✅
test_kv_i8_cache	11/11	L4 cache	—
test_hrr_cleanup	5/5	L5	—
test_hrr_attention	5/5	L5	—
test_hrr_properties	3/3 (phasor recovery, Parseval)	L5	✅
test_dense_is_default	3/3	D1 enforcement	—
test_acdc_rect	—	ACDC rectangular	—
test_adaptive_k	—	Adaptive sparse	—
test_rag_retrieval	—	L6 RAG	—
test_extract_acdc_diagonal (Python)	4/4	L3 closed form	—

Plus snapshot baselines and air-gapped boot validation.

Part of a split from original PR #567. This is the test portion — depends on the kernel code from #570.

[Peder Munksgaard (peder1981)]

Conteúdo mesclado no PR #570 (kernels + tests + CI auto-contido). Este PR é encerrado como duplicado.