fix(ci): install client from release branch before uv sync (#4001)

Fixes CI failures on release branches where uv sync can't resolve RC
dependencies.

The problem: on release branches like `release-0.3.x`, pyproject.toml
requires `llama-stack-client>=0.3.1rc1`. But RC versions only exist on
test.pypi, not PyPI. So uv sync fails before we even get a chance to
install the client from git.

The fix is simple - on release branches, pre-install the client from the
matching git branch first, then run uv sync. This satisfies the RC
requirement and lets dependency resolution succeed.

Modified setup-runner and pre-commit workflows to do this. Also cleaned
up some duplicate logic in setup-test-environment that's now handled
centrally.

Example failure:
5415478835

.github/workflows/pre-commit.yml

@@ -130,8 +130,22 @@ jobs:
             exit 1
           fi
 
+      - name: Configure client installation
+        id: client-config
+        uses: ./.github/actions/install-llama-stack-client
+
       - name: Sync dev + type_checking dependencies
-        run: uv sync --group dev --group type_checking
+        env:
+          UV_INDEX_URL: ${{ steps.client-config.outputs.uv-index-url }}
+          UV_EXTRA_INDEX_URL: ${{ steps.client-config.outputs.uv-extra-index-url }}
+        run: |
+          uv sync --group dev --group type_checking
+
+          # Install specific client version after sync if needed
+          if [ "${{ steps.client-config.outputs.install-after-sync }}" = "true" ]; then
+            echo "Installing llama-stack-client from: ${{ steps.client-config.outputs.install-source }}"
+            uv pip install ${{ steps.client-config.outputs.install-source }}
+          fi
 
       - name: Run mypy (full type_checking)
         run: |