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.

.pre-commit-config.yaml

@@ -52,10 +52,6 @@ repos:
         additional_dependencies:
         - black==24.3.0
 
--   repo: https://github.com/astral-sh/uv-pre-commit
-    rev: 0.7.20
-    hooks:
-    -   id: uv-lock
 
 -   repo: https://github.com/pre-commit/mirrors-mypy
     rev: v1.16.1
@@ -78,11 +74,20 @@ repos:
 
 -   repo: local
     hooks:
+      - id: uv-lock
+        name: uv-lock
+        additional_dependencies:
+          - uv==0.7.20
+        entry: ./scripts/uv-run-with-index.sh lock
+        language: python
+        pass_filenames: false
+        require_serial: true
+        files: ^(pyproject\.toml|uv\.lock)$
       - id: distro-codegen
         name: Distribution Template Codegen
         additional_dependencies:
           - uv==0.7.8
-        entry: uv run --group codegen ./scripts/distro_codegen.py
+        entry: ./scripts/uv-run-with-index.sh run --group codegen ./scripts/distro_codegen.py
         language: python
         pass_filenames: false
         require_serial: true
@@ -91,7 +96,7 @@ repos:
         name: Provider Codegen
         additional_dependencies:
           - uv==0.7.8
-        entry: uv run --group codegen ./scripts/provider_codegen.py
+        entry: ./scripts/uv-run-with-index.sh run --group codegen ./scripts/provider_codegen.py
         language: python
         pass_filenames: false
         require_serial: true
@@ -100,7 +105,7 @@ repos:
         name: API Spec Codegen
         additional_dependencies:
           - uv==0.7.8
-        entry: sh -c 'uv run ./docs/openapi_generator/run_openapi_generator.sh > /dev/null'
+        entry: sh -c './scripts/uv-run-with-index.sh run ./docs/openapi_generator/run_openapi_generator.sh > /dev/null'
         language: python
         pass_filenames: false
         require_serial: true
@@ -141,7 +146,7 @@ repos:
         name: Generate CI documentation
         additional_dependencies:
           - uv==0.7.8
-        entry: uv run ./scripts/gen-ci-docs.py
+        entry: ./scripts/uv-run-with-index.sh run ./scripts/gen-ci-docs.py
         language: python
         pass_filenames: false
         require_serial: true