Fix CI: platform-specific Python setup and artifact actions v3 for Gitea

- Use actions/setup-python only on Linux (container); macOS/Windows create
  a venv from pre-installed python3.12 to avoid privileged install failures
- Downgrade upload/download-artifact to v3 (v4 uses an API Gitea doesn't support)
- Remove merge-multiple (v4-only option) from download-artifact
- Change release files glob to artifacts/**/* (v3 nests each artifact in a subdir)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.github/workflows/release.yml

@@ -31,11 +31,26 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
 
-      - name: Set up Python 3.12
+      - name: Set up Python 3.12 (Linux)
+        if: runner.os == 'Linux'
         uses: actions/setup-python@v5
         with:
           python-version: "3.12"
 
+      - name: Set up Python venv (macOS)
+        if: runner.os == 'macOS'
+        run: |
+          PYBIN="$(command -v python3.12 || echo /opt/homebrew/bin/python3.12)"
+          "$PYBIN" -m venv .venv
+          echo "$PWD/.venv/bin" >> "$GITHUB_PATH"
+
+      - name: Set up Python venv (Windows)
+        if: runner.os == 'Windows'
+        shell: pwsh
+        run: |
+          py -3.12 -m venv .venv
+          Add-Content -Path $env:GITHUB_PATH -Value "$env:GITHUB_WORKSPACE\.venv\Scripts"
+
       - name: Install dependencies
         run: pip install -r requirements-dev.txt
 
@@ -75,7 +90,7 @@ jobs:
       # ── Upload artifact for the release job ──────────────────────────────
 
       - name: Upload artifact
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v3
         with:
           name: ${{ matrix.artifact }}
           path: ${{ matrix.artifact }}
@@ -93,10 +108,9 @@ jobs:
 
     steps:
       - name: Download all artifacts
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v3
         with:
           path: artifacts
-          merge-multiple: true
 
       - name: Create GitHub Release
         uses: softprops/action-gh-release@v2
@@ -105,7 +119,7 @@ jobs:
           draft: false
           prerelease: false
           generate_release_notes: true
-          files: artifacts/*
+          files: artifacts/**/*
           body: |
             ## Better Claude Config ${{ github.ref_name }}