Add Linux build to CI (Ubuntu 22.04 x64) + README download links

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/workflows/build.yml

@@ -84,9 +84,49 @@ jobs:
           name: InstaDrums-Standalone-macOS
           path: InstaDrums-Standalone-macOS.zip
 
+  build-linux:
+    runs-on: ubuntu-22.04
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y build-essential cmake git libasound2-dev \
+            libfreetype6-dev libx11-dev libxrandr-dev libxcursor-dev \
+            libxinerama-dev libwebkit2gtk-4.1-dev libcurl4-openssl-dev
+
+      - name: Clone JUCE
+        run: git clone --depth 1 https://github.com/juce-framework/JUCE.git ../JUCE
+
+      - name: Configure CMake
+        run: cmake -B build -DCMAKE_BUILD_TYPE=Release
+
+      - name: Build Release
+        run: cmake --build build --config Release --parallel $(nproc)
+
+      - name: Package VST3
+        working-directory: build/InstaDrums_artefacts/Release
+        run: zip -r $GITHUB_WORKSPACE/InstaDrums-VST3-Linux-x64.zip VST3/InstaDrums.vst3
+
+      - name: Package Standalone
+        run: zip -j InstaDrums-Standalone-Linux-x64.zip build/InstaDrums_artefacts/Release/Standalone/InstaDrums
+
+      - name: Upload VST3
+        uses: actions/upload-artifact@v4
+        with:
+          name: InstaDrums-VST3-Linux-x64
+          path: InstaDrums-VST3-Linux-x64.zip
+
+      - name: Upload Standalone
+        uses: actions/upload-artifact@v4
+        with:
+          name: InstaDrums-Standalone-Linux-x64
+          path: InstaDrums-Standalone-Linux-x64.zip
+
   release:
     if: startsWith(github.ref, 'refs/tags/v')
-    needs: [build-windows, build-macos]
+    needs: [build-windows, build-macos, build-linux]
     runs-on: ubuntu-latest
     permissions:
       contents: write
@@ -105,4 +145,6 @@ jobs:
             artifacts/InstaDrums-VST3-macOS/InstaDrums-VST3-macOS.zip
             artifacts/InstaDrums-AU-macOS/InstaDrums-AU-macOS.zip
             artifacts/InstaDrums-Standalone-macOS/InstaDrums-Standalone-macOS.zip
+            artifacts/InstaDrums-VST3-Linux-x64/InstaDrums-VST3-Linux-x64.zip
+            artifacts/InstaDrums-Standalone-Linux-x64/InstaDrums-Standalone-Linux-x64.zip
           generate_release_notes: true