v6.4.10: Multi-threading in Python 3.13t

Other minor tweaks:

• bf16 L2 calculation in Rust
• flushing denormals in Rust
• nonnull build warnings in GCC & Clang
• upgrading JS dependencies

Patch

• Fix: Require NumPy for GIL tests (529b0dd)
• Improve: Free threading examples & checks (83e522a)
• Make: Enable free-threading CIBW builds (0093c3f)
• Docs: Setting up uv env (8dc7012)
• Improve: GIL-free batch-processing in Py (eb234d5)
• Make: Drop Python 3.7 for 3.13t (fc62de4)
• Improve: Flushing denormals in Rust (1c1e608)
• Docs: Top-level script instructions (d17c9a9)
• Fix: Typos & auto-formatting (7bca0e3)
• Make: Bump JS deps (440d3e5)
• Fix: Avoid nonull attribute warning on GCC (f14db4a)
• Fix: Wrong SpatialSimilarity::<bf16>::l2 dispatch (00ad454)