fix(ci): use test.pypi as extra index for RC dependencies (#4009)

Backports UV index configuration fixes from `release-0.3.x` (PR #4002). 

The main issue: when we created the release branch infrastructure, we
configured UV to use `test.pypi` as the PRIMARY index to resolve RC
dependencies. This caused UV to look for ALL packages there first, which
led to problems - some packages don't have binary wheels on `test.pypi`,
so UV tried building from source and failed (like the `psycopg2-binary`
issue we hit).

The fix is simple: use PyPI as primary (default) and `test.pypi` as an
EXTRA index. UV will check PyPI first for everything, and only fall back
to `test.pypi` for packages not found there (like our RC client
versions).

This PR includes:
- Fixed `install-llama-stack-client` action to output
`UV_EXTRA_INDEX_URL` instead of `UV_INDEX_URL`
- New `uv-run-with-index.sh` wrapper that auto-detects release branches
and sets UV env vars
- Updated pre-commit hooks (`uv-lock`, codegen, etc.) to use the wrapper
- Pass UV env vars as Docker build args in all locations
- Scope UV env vars properly in Containerfile (inline for llama-stack
install, explicitly unset before distribution deps)
- Export UV env vars to `GITHUB_ENV` in setup-runner for cross-step
persistence

The wrapper detects release branches automatically in both CI and local
environments, so this "just works" without manual configuration. On main
(non-release branch), the wrapper becomes a no-op.

Tested and validated on `release-0.3.x` where all CI checks pass.

.github/actions/setup-runner/action.yml

@@ -27,9 +27,15 @@ runs:
     - name: Install dependencies
       shell: bash
       env:
-        UV_INDEX_URL: ${{ steps.client-config.outputs.uv-index-url }}
         UV_EXTRA_INDEX_URL: ${{ steps.client-config.outputs.uv-extra-index-url }}
       run: |
+        # Export UV env vars to GITHUB_ENV so they persist across steps
+        if [ -n "$UV_EXTRA_INDEX_URL" ]; then
+          echo "UV_EXTRA_INDEX_URL=$UV_EXTRA_INDEX_URL" >> $GITHUB_ENV
+          echo "UV_INDEX_STRATEGY=unsafe-best-match" >> $GITHUB_ENV
+          echo "Exported UV environment variables for subsequent steps"
+        fi
+
         echo "Updating project dependencies via uv sync"
         uv sync --all-groups