add release workflow for tagged versions

- trigger builds on version tags (v*)
- create GitHub release with all platform binaries
- include SHA256 checksums file
- auto-generate release notes

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: MagicalTux

.github/workflows/build.yml

@@ -3,6 +3,8 @@ name: Build and Test
 on:
   push:
     branches: [master, main]
+    tags:
+      - 'v*'
   pull_request:
     branches: [master, main]
 
@@ -198,3 +200,40 @@ jobs:
         with:
           name: shells-go-darwin-universal
           path: shells-go-darwin-universal
+
+  release:
+    name: Create Release
+    runs-on: ubuntu-latest
+    needs: [build-linux, build-windows, build-macos-arm]
+    if: startsWith(github.ref, 'refs/tags/')
+    permissions:
+      contents: write
+    steps:
+      - name: Download all artifacts
+        uses: actions/download-artifact@v4
+        with:
+          path: artifacts
+
+      - name: Prepare release assets
+        run: |
+          mkdir -p release
+          cp artifacts/shells-go-linux-amd64/shells-go-linux-amd64 release/
+          cp artifacts/shells-go-windows-amd64/shells-go-windows-amd64.exe release/
+          cp artifacts/shells-go-darwin-amd64/shells-go-darwin-amd64 release/
+          cp artifacts/shells-go-darwin-arm64/shells-go-darwin-arm64 release/
+          cp artifacts/shells-go-darwin-universal/shells-go-darwin-universal release/
+          cd release
+          sha256sum * > checksums.txt
+
+      - name: Create Release
+        uses: softprops/action-gh-release@v2
+        with:
+          draft: false
+          generate_release_notes: true
+          files: |
+            release/shells-go-linux-amd64
+            release/shells-go-windows-amd64.exe
+            release/shells-go-darwin-amd64
+            release/shells-go-darwin-arm64
+            release/shells-go-darwin-universal
+            release/checksums.txt