ci: add release pipeline with NuGet packaging and quality gates

Triggered by tag push (v*) or manual dispatch. Validates semver tag format,
runs build, test, and format check, then packs NuGet package with version
from tag and creates GitHub Release with artifacts attached.

Co-Authored-By: Svrnty Inc. <eng@svrnty.com>

.github/workflows/release.yml

@@ -0,0 +1,86 @@
+name: Release
+
+on:
+  push:
+    tags: ["v*"]
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: "Release tag (e.g. v1.2.0)"
+        required: true
+        type: string
+
+concurrency:
+  group: release-${{ github.ref }}
+  cancel-in-progress: false
+
+permissions:
+  contents: write
+
+jobs:
+  release:
+    name: Validate, Build, Pack & Release
+    runs-on: ubuntu-latest
+    steps:
+      - name: Resolve tag
+        id: tag
+        run: |
+          if [[ "${{ github.event_name }}" == "push" ]]; then
+            TAG="${GITHUB_REF_NAME}"
+          else
+            TAG="${{ inputs.tag }}"
+          fi
+
+          if [[ ! "$TAG" =~ ^v[0-9]+\.[0-9]+\.[0-9]+([.-][0-9A-Za-z.-]+)?$ ]]; then
+            echo "::error::Tag must match semver format (vX.Y.Z[-suffix]): got ${TAG}"
+            exit 1
+          fi
+
+          echo "tag=${TAG}" >> "$GITHUB_OUTPUT"
+          echo "version=${TAG#v}" >> "$GITHUB_OUTPUT"
+
+      - uses: actions/checkout@v4
+        with:
+          ref: ${{ steps.tag.outputs.tag }}
+
+      - uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: "10.0.x"
+
+      - name: Restore
+        run: dotnet restore Svrnty.CQRS.sln
+
+      - name: Build
+        run: dotnet build Svrnty.CQRS.sln --no-restore --configuration Release --warnaserror
+
+      - name: Test
+        run: dotnet test Svrnty.CQRS.sln --no-build --configuration Release --verbosity normal
+
+      - name: Format check
+        run: dotnet format Svrnty.CQRS.sln --verify-no-changes
+
+      - name: Pack NuGet packages
+        run: |
+          dotnet pack Svrnty.CQRS.sln \
+            --no-build \
+            --configuration Release \
+            --output ./artifacts \
+            -p:Version=${{ steps.tag.outputs.version }}
+
+      - name: Upload NuGet artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: nuget-packages
+          path: ./artifacts/*.nupkg
+          retention-days: 30
+
+      - name: Create GitHub Release
+        uses: softprops/action-gh-release@v2
+        with:
+          tag_name: ${{ steps.tag.outputs.tag }}
+          generate_release_notes: true
+          files: |
+            artifacts/*.nupkg
+            artifacts/*.snupkg
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}