feat: cross-build Windows ZIP from Linux CI runner

Replace Windows runner requirement with cross-compilation:
download Windows embedded Python + win_amd64 wheels from PyPI,
package into the same ZIP structure as build-dist.ps1.

All 4 release jobs now run on ubuntu-latest.

.gitea/workflows/release.yml

@@ -40,25 +40,35 @@ jobs:
           echo "release_id=$RELEASE_ID" >> "$GITHUB_OUTPUT"
           echo "Created release ID: $RELEASE_ID"
 
-  # ── Windows portable ZIP ───────────────────────────────────
+  # ── Windows portable ZIP (cross-built from Linux) ─────────
   build-windows:
     needs: create-release
-    runs-on: windows-latest
+    runs-on: ubuntu-latest
     steps:
       - name: Checkout
         uses: actions/checkout@v4
         with:
           fetch-depth: 0
 
+      - name: Setup Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.11'
+
       - name: Setup Node.js
         uses: actions/setup-node@v4
         with:
           node-version: '20'
 
-      - name: Build portable distribution
-        shell: pwsh
+      - name: Install system dependencies
         run: |
-          .\build-dist.ps1 -Version "${{ gitea.ref_name }}"
+          sudo apt-get update
+          sudo apt-get install -y --no-install-recommends zip libportaudio2
+
+      - name: Cross-build Windows distribution
+        run: |
+          chmod +x build-dist-windows.sh
+          ./build-dist-windows.sh "${{ gitea.ref_name }}"
 
       - name: Upload build artifact
         uses: actions/upload-artifact@v3
@@ -68,7 +78,6 @@ jobs:
           retention-days: 90
 
       - name: Attach ZIP to release
-        shell: bash
         env:
           GITEA_TOKEN: ${{ secrets.GITEA_TOKEN }}
         run: |