P9 (WIP): compiled kernels (rust/simurg-core, PyO3) with bit-identical pure-Python fallback

Rust ports of the hot paths found by profiling: fused per-locus GenCall calling
and scoring, BAF/LRR, libm maps with CPython math semantics, both nearest-neighbour
searches of the normalization fit, and the BPM LocusEntry parser. Address
coverage is memoised per IDAT layout. SIMURG_PURE_PYTHON=1 forces the pure paths.
On the Pi: genotype_sample 3.4 s -> 1.1 s, 36-sample GSA run 131 s -> 46 s, BPM
read 4x faster; 36 GSA + 6 Omni2.5 GTCs and QC tables byte-identical to the pure
path; tests/unit/test_core_kernels.py checks every kernel on edge cases.
bench/profile_genotype.py, bench/scaling.py, cloud task p9 (thread scaling).

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01814GKVzZVL3FuF3DeiZXhv

rust/simurg-core/pyproject.toml

@@ -0,0 +1,14 @@
+[build-system]
+requires = ["maturin>=1.7,<2"]
+build-backend = "maturin"
+
+[project]
+name = "simurg-core"
+description = "Compiled kernels for SimurgArray (optional; the pure-Python paths give identical results)"
+requires-python = ">=3.12"
+license = { text = "MIT" }
+dependencies = ["numpy>=1.26"]
+dynamic = ["version"]
+
+[tool.maturin]
+features = ["pyo3/extension-module"]