feat!: migrate native extension from C to Rust (#44)

* feat!: migrate native extension from C to Rust

Complete rewrite of the native extension using Rust and the Magnus crate
instead of C. This maintains the same public API while providing better
memory safety and modern tooling.

- Replace all C source files with Rust implementation
- Add Cargo workspace and build configuration
- Update gem specification for Rust compilation
- Modernize codebase with frozen string literals
- Update CI pipeline to support Rust builds
- Bump version to 2.0.0-pre for major release

BREAKING CHANGE: Build system now requires Rust toolchain instead of C compiler

* Update ext/ruby_native_statistics/src/lib.rs

Co-authored-by: Copilot <[email protected]>

* refactor: use slice-based helpers to reduce code duplication in variance/stdev functions

- Add calculate_variance() and calculate_stdev() helper functions that work with slices
- Eliminate duplicated variance calculation logic across var, stdev, varp, stdevp functions
- Use population parameter to distinguish between sample and population statistics
- Replace length == 0.0 checks with more idiomatic array.is_empty()
- Maintain Vec usage only where necessary (median, percentile need sorting)

---------

Co-authored-by: Copilot <[email protected]>

Author: corybuecker

.github/workflows/main.yml

@@ -3,24 +3,24 @@ name: Test suite
 on:
   - push
 
-env:
-  CI: true
-
 jobs:
   run-tests:
     name: Run tests
-    runs-on: ubuntu-latest
     strategy:
       matrix:
+        os:
+          - ubuntu-latest
+          - macos-latest
         ruby:
-          - 3.2.6
-          - 3.3.7
-          - 3.4.1
+          - 3.2.8
+          - 3.3.8
+          - 3.4.4
+    runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
       - uses: ruby/setup-ruby@a9bfc2ecf3dd40734a9418f89a7e9d484c32b990
         with:
           ruby-version: ${{ matrix.ruby }}
-      - run: gem install bundler --version 2.6.3 --no-document
+      - run: gem install bundler --version 2.7.0 --no-document
       - run: bundle
       - run: rake

.gitignore

@@ -55,4 +55,7 @@ build-iPhoneSimulator/
 # Used by RuboCop. Remote config files pulled in from inherit_from directive.
 # .rubocop-https?--*
 
-*.bundle
+*.bundle
+
+/ext/ruby_native_statistics/target
+/target

Cargo.lock

@@ -0,0 +1,3 @@
+[workspace]
+members = ["./ext/ruby_native_statistics"]
+resolver = "3"