release: prepare cChardet 2.3.0

[PyYoshi]

Summary

Prepare cChardet 2.3.0 for release.

• set the public package version to 2.3.0
• finalize the 2.3.0 changelog with the 2026-09-16 release date

Highlights

• support free-threaded CPython 3.14 without re-enabling the GIL
• ship cp314t wheels across Linux, macOS, and Windows targets
• reduce direct uchardet detection time by roughly 52–56% in the documented native benchmarks
• cache repeated language-model and candidate analysis work
• reuse SBCS filtering storage for incremental input
• add reproducible native and free-threaded performance benchmarks

Local validation

• UV_CACHE_DIR=/tmp/cchardet-uv-cache make check
  • Ruff passed
  • strict mypy passed
  • 29 pytest tests passed
• uv lock --check passed
• uv build produced cchardet-2.3.0.tar.gz and a 2.3.0 wheel
• twine check passed for both distributions
• the wheel installed into a clean uv-managed CPython 3.14 environment
• installed-wheel smoke test passed
• cchardet.__version__ == "2.3.0" and cchardet.version == (2, 3, 0)

After merge, create and push a signed v2.3.0 tag. The tag workflow will build all platform wheels, publish through the protected PyPI Trusted Publisher environment, and attach attestations.