ci: add cross-platform GitHub Actions builds (Win/macOS/Linux) + tests & release on tags

- Adds .github/workflows/build.yml
- Runs pytest on ubuntu-latest, windows-latest, macos-13 (x64) and macos-14 (arm64)
- Builds unsigned binaries with PyInstaller from yt_audio_workbench.spec
- Uploads zips as artifacts per OS
- On tags v*, creates a GitHub Release and attaches artifacts
- Installs python3-tk on Ubuntu runners for Tkinter

Author: MitCode85

.github/workflows/build.yml

@@ -0,0 +1,110 @@
+name: Build (Windows/macOS/Linux)
+
+on:
+  push:
+    branches: [ main, master ]
+    paths:
+      - '**/*.py'
+      - 'lang/**'
+      - 'HELP.md'
+      - 'yt_audio_workbench.spec'
+      - '.github/workflows/build.yml'
+  pull_request:
+    branches: [ main, master ]
+  workflow_dispatch:
+  tags:
+    - 'v*'
+
+jobs:
+  test:
+    name: Tests (${{ matrix.os }} | py${{ matrix.python }})
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-13, macos-14]
+        python: ['3.11']
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python }}
+      - name: Install OS dependencies (Linux only)
+        if: startsWith(matrix.os, 'ubuntu')
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y python3-tk
+      - name: Install Python deps
+        run: |
+          if [ -f requirements.txt ]; then python -m pip install -r requirements.txt; fi
+          python -m pip install --upgrade pip
+          python -m pip install pytest
+      - name: Run tests
+        run: pytest -q
+
+  build:
+    name: Build (${{ matrix.os }})
+    needs: test
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-13, macos-14]
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.11'
+      - name: Install OS dependencies (Linux only)
+        if: startsWith(matrix.os, 'ubuntu')
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y python3-tk
+      - name: Install Python deps
+        run: |
+          if [ -f requirements.txt ]; then python -m pip install -r requirements.txt; fi
+          python -m pip install --upgrade pip
+          python -m pip install pyinstaller
+      - name: Build with PyInstaller
+        run: |
+          pyinstaller -y yt_audio_workbench.spec
+      - name: Pack artifact (Windows)
+        if: startsWith(matrix.os, 'windows')
+        shell: pwsh
+        run: |
+          $ErrorActionPreference = 'Stop'
+          $zip = "YT-Audio-Workbench-Windows.zip"
+          Compress-Archive -Path "dist\YT-Audio-Workbench\*" -DestinationPath $zip
+          echo "ZIP_NAME=$zip" >> $env:GITHUB_ENV
+      - name: Pack artifact (macOS/Linux)
+        if: startsWith(matrix.os, 'macos') || startsWith(matrix.os, 'ubuntu')
+        run: |
+          cd dist
+          zip -r ../YT-Audio-Workbench-${{ runner.os }}.zip YT-Audio-Workbench
+          echo "ZIP_NAME=YT-Audio-Workbench-${{ runner.os }}.zip" >> $GITHUB_ENV
+      - name: Upload artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: YT-Audio-Workbench-${{ matrix.os }}
+          path: ${{ env.ZIP_NAME }}
+
+  release:
+    name: Release on tag
+    if: startsWith(github.ref, 'refs/tags/v')
+    needs: build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/download-artifact@v4
+        with:
+          path: artifacts
+      - name: List artifacts
+        run: ls -R artifacts
+      - name: Create GitHub Release
+        uses: softprops/action-gh-release@v2
+        with:
+          draft: false
+          prerelease: false
+          files: |
+            artifacts/**/YT-Audio-Workbench-*.zip
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}