feat(python): add native distribution and release infrastructure

- add the Rust-backed Python API with PyStemmer compatibility
- distribute standard compiled models as a separate Python package
- generate model artifacts during builds instead of storing them in Git
- add GitHub release and Pages-backed package index workflows
- add Python tests, benchmarks, documentation, and Gradle integration
- refresh the documentation site, branding, and language benchmarks

python/benchmarks/requirements-bench.txt

@@ -0,0 +1,6 @@
+# Optional comparison engines for the runtime stemming benchmark.
+# radixor itself must already be built (maturin develop) in the same env.
+# Any subset may be installed; the harness auto-detects what is present.
+PyStemmer          # Snowball as a C extension (libstemmer); real batch API
+snowballstemmer    # Official pure-Python Snowball (used via its pure backend)
+nltk               # Porter (English) pure-Python reference baseline