Remove Windows builds and tests from CI

Windows support is removed from CI workflows:
- Removed windows-latest from test matrix
- Removed x86_64-pc-windows-msvc from build targets
- Simplified artifact upload path (no .exe conditional)

CI now only runs on Ubuntu and macOS.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -57,7 +57,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-latest, macos-latest, windows-latest]
+        os: [ubuntu-latest, macos-latest]
         rust: [stable, beta]
     steps:
       - name: Checkout code
@@ -114,8 +114,6 @@ jobs:
             target: x86_64-apple-darwin
           - os: macos-latest
             target: aarch64-apple-darwin
-          - os: windows-latest
-            target: x86_64-pc-windows-msvc
     steps:
       - name: Checkout code
         uses: actions/checkout@v4
@@ -154,8 +152,7 @@ jobs:
         uses: actions/upload-artifact@v4
         with:
           name: piglet-${{ matrix.target }}
-          path: |
-            target/${{ matrix.target }}/release/piglet${{ matrix.os == 'windows-latest' && '.exe' || '' }}
+          path: target/${{ matrix.target }}/release/piglet
 
   security-audit:
     name: Security Audit