fix(ci): install client from release branch before uv sync (#4002)

Backport of #4001 to release-0.3.x branch.

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`. RC versions only exist on test.pypi, not
PyPI. This causes multiple CI failures:

1. `uv sync` fails because it can't resolve RC versions from PyPI
2. pre-commit hooks (uv-lock, codegen) fail for the same reason  
3. mypy workflow section needs uv installed

## The Solution

Configure UV to use test.pypi when on release branches:

- Set `UV_INDEX_URL=https://test.pypi.org/simple/` (primary)
- Set `UV_EXTRA_INDEX_URL=https://pypi.org/simple/` (fallback)
- Set `UV_INDEX_STRATEGY=unsafe-best-match` to check both indexes

This allows `uv sync` to resolve common packages from PyPI and RC
versions from test.pypi.

## Additional Fixes

- Export UV env vars to `GITHUB_ENV` so pre-commit hooks inherit them
- Install uv in pre-commit workflow for mypy section
- Handle missing `type_checking` dependency group on release-0.3.x
- Regenerate uv.lock with RC versions for the release branch

## Changes

- Created reusable `install-llama-stack-client` action for configuration
- Modified `setup-runner` to set UV environment variables before sync
- Modified `pre-commit` workflow to configure client and export env vars
- Updated uv.lock with RC versions from test.pypi

This is a cherry-pick of commits afa9f0882, c86e6e906, 626639bee, and
081566321 from main, plus additional fixes for release branch
compatibility.

containers/Containerfile

@@ -19,6 +19,8 @@ ARG KEEP_WORKSPACE=""
 ARG DISTRO_NAME="starter"
 ARG RUN_CONFIG_PATH=""
 ARG UV_HTTP_TIMEOUT=500
+ARG UV_EXTRA_INDEX_URL=""
+ARG UV_INDEX_STRATEGY=""
 ENV UV_HTTP_TIMEOUT=${UV_HTTP_TIMEOUT}
 ENV PYTHONDONTWRITEBYTECODE=1
 ENV PIP_DISABLE_PIP_VERSION_CHECK=1
@@ -72,13 +74,19 @@ RUN set -eux; \
     fi;
 
 # Install llama-stack
+# Use UV_EXTRA_INDEX_URL inline only for this step to avoid affecting distribution deps
 RUN set -eux; \
     if [ "$INSTALL_MODE" = "editable" ]; then \
         if [ ! -d "$LLAMA_STACK_DIR" ]; then \
             echo "INSTALL_MODE=editable requires LLAMA_STACK_DIR to point to a directory inside the build context" >&2; \
             exit 1; \
         fi; \
-        uv pip install --no-cache-dir -e "$LLAMA_STACK_DIR"; \
+        if [ -n "$UV_EXTRA_INDEX_URL" ] && [ -n "$UV_INDEX_STRATEGY" ]; then \
+            UV_EXTRA_INDEX_URL="$UV_EXTRA_INDEX_URL" UV_INDEX_STRATEGY="$UV_INDEX_STRATEGY" \
+                uv pip install --no-cache-dir -e "$LLAMA_STACK_DIR"; \
+        else \
+            uv pip install --no-cache-dir -e "$LLAMA_STACK_DIR"; \
+        fi; \
     elif [ "$INSTALL_MODE" = "test-pypi" ]; then \
         uv pip install --no-cache-dir fastapi libcst; \
         if [ -n "$TEST_PYPI_VERSION" ]; then \
@@ -95,7 +103,9 @@ RUN set -eux; \
     fi;
 
 # Install the dependencies for the distribution
+# Explicitly unset UV index env vars to ensure we only use PyPI for distribution deps
 RUN set -eux; \
+    unset UV_EXTRA_INDEX_URL UV_INDEX_STRATEGY; \
     if [ -z "$DISTRO_NAME" ]; then \
         echo "DISTRO_NAME must be provided" >&2; \
         exit 1; \