CI: pre-install http-ece with --no-build-isolation to fix PEP 517 isolation

pip builds legacy setup.py packages in an isolated environment that doesn't
inherit the globally installed setuptools. Pre-building http-ece with
--no-build-isolation bypasses that isolation so setuptools is available.

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

.forgejo/workflows/ci.yml

@@ -86,8 +86,10 @@ jobs:
           apt-get install -y -qq python3.12 python3.12-dev python3.12-venv python3-pip git
           python3.12 -m ensurepip --upgrade
 
-      - name: Install setuptools (required by legacy deps)
-        run: python3.12 -m pip install setuptools
+      - name: Install setuptools and pre-build legacy deps
+        run: |
+          python3.12 -m pip install setuptools wheel
+          python3.12 -m pip install --no-build-isolation http-ece
 
       - name: Install package with dev deps
         run: python3.12 -m pip install -e ".[dev]"