refactor: consolidate all client install logic into single action

Renamed install-client-for-release to install-llama-stack-client and
made it handle both release branches and client-version inputs. Now
all client installation logic lives in one place:

- Release branches: always install from matching git branch
- Non-release branches: install based on client-version input

This eliminates all the conditional logic from setup-runner.

.github/actions/install-client-for-release/action.yml

@@ -1,34 +0,0 @@
-name: Install Client for Release Branch
-description: Pre-install llama-stack-client from git on release branches to satisfy RC dependencies before uv sync
-
-runs:
-  using: "composite"
-  steps:
-    - name: Install client from release branch if needed
-      shell: bash
-      run: |
-        # Determine the branch we're working with
-        # For PRs: use base_ref (target branch)
-        # For pushes: use ref (current branch)
-        BRANCH="${{ github.base_ref || github.ref }}"
-        BRANCH="${BRANCH#refs/heads/}"  # Strip refs/heads/ prefix
-
-        echo "Working with branch: $BRANCH"
-
-        # If on a release branch, install from matching release branch BEFORE uv sync
-        # This allows uv sync to resolve dependencies that reference unreleased RC versions
-        # We always do this on release branches regardless of client-version to satisfy pyproject.toml
-        if [[ "$BRANCH" =~ ^release-[0-9]+\.[0-9]+\.x$ ]]; then
-          echo "Detected release branch: $BRANCH"
-          echo "Checking if matching branch exists in llama-stack-client-python..."
-
-          # Check if the branch exists in the client repo
-          if git ls-remote --exit-code --heads https://github.com/llamastack/llama-stack-client-python.git "$BRANCH" > /dev/null 2>&1; then
-            echo "Installing llama-stack-client-python from matching branch: $BRANCH"
-            uv pip install git+https://github.com/llamastack/llama-stack-client-python.git@$BRANCH
-          else
-            echo "::error::Branch $BRANCH not found in llama-stack-client-python repository"
-            echo "::error::Please create the matching release branch in llama-stack-client-python before testing"
-            exit 1
-          fi
-        fi