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).

.github/workflows/ci.yml

@@ -23,3 +23,9 @@ jobs:
         run: uv run mypy
       - name: Unit tests (no downloaded data needed)
         run: uv run pytest tests/unit -q
+      - name: Build the compiled kernels (rust/simurg-core)
+        run: |
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --profile minimal
+          PATH="$HOME/.cargo/bin:$PATH" uv pip install ./rust/simurg-core
+      - name: Unit tests with the compiled kernels (must equal the pure-Python results)
+        run: uv run pytest tests/unit -q