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

Backport UV index configuration fixes from release-0.3.x that enable
resolution of RC dependencies from test.pypi while keeping PyPI as the
primary index.

Key changes:
- Fix install-llama-stack-client action to use test.pypi as EXTRA index
  (not primary) to prevent UV from looking for all packages there first
- Add uv-run-with-index.sh wrapper that auto-detects release branches
  and sets UV env vars for local pre-commit hooks
- Update pre-commit hooks to use the wrapper for all uv commands
- Add UV_INDEX_STRATEGY=unsafe-best-match to allow checking multiple indexes
- Pass UV env vars as Docker build args and use them inline only for
  llama-stack installation to avoid affecting distribution deps
- Export UV env vars to GITHUB_ENV in setup-runner for cross-step persistence

This infrastructure allows future release branches to work correctly
without manual UV configuration.

scripts/docker.sh

@@ -215,6 +215,16 @@ build_image() {
         --build-arg "LLAMA_STACK_DIR=/workspace"
     )
 
+    # Pass UV index configuration for release branches
+    if [[ -n "${UV_EXTRA_INDEX_URL:-}" ]]; then
+        echo "Adding UV_EXTRA_INDEX_URL to docker build: $UV_EXTRA_INDEX_URL"
+        build_cmd+=(--build-arg "UV_EXTRA_INDEX_URL=$UV_EXTRA_INDEX_URL")
+    fi
+    if [[ -n "${UV_INDEX_STRATEGY:-}" ]]; then
+        echo "Adding UV_INDEX_STRATEGY to docker build: $UV_INDEX_STRATEGY"
+        build_cmd+=(--build-arg "UV_INDEX_STRATEGY=$UV_INDEX_STRATEGY")
+    fi
+
     if ! "${build_cmd[@]}"; then
         echo "❌ Failed to build Docker image"
         exit 1