fix(ci): add missing protobuf and workspace setup steps

Several workflows were missing required setup steps:

1. kfp-sdk-client-tests.yml: Added protobuf action and workspace
   packages installation before running tests

2. gcpc-modules-tests.yml: Replaced manual protobuf-compiler installation
   with protobuf action, added workspace packages installation

3. readthedocs-builds.yml: Added protobuf action instead of manual
   make command

4. components/test_load_all_components.sh: Changed python3 to uv run
   python to use the correct virtual environment

5. setup-python/action.yml: Updated to actions/setup-python@v6 for
   consistency with other workflows

Author: sh4shv4t

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

@@ -12,7 +12,7 @@ runs:
   using: "composite"
   steps:
     - name: Set up Python
-      uses: actions/setup-python@v5
+      uses: actions/setup-python@v6
       with:
         python-version: ${{ inputs.python-version }}
 

.github/workflows/gcpc-modules-tests.yml

@@ -23,12 +23,12 @@ jobs:
         with:
           python-version: '3.9'
 
-      - name: Install protobuf-compiler
-        run: sudo apt update && sudo apt install -y protobuf-compiler
+      - name: Install protobuf dependencies & generate proto files
+        uses: ./.github/actions/protobuf
 
-      - name: Generate API proto files
-        working-directory: ./api
-        run: make clean python
+      - name: Install workspace packages
+        run: |
+          uv pip install --no-deps -e sdk/python -e api/v2alpha1/python -e kubernetes_platform/python -e backend/api/v2beta1/python_http_client
 
       - name: Install google-cloud component
         run: uv pip install components/google-cloud

.github/workflows/kfp-sdk-client-tests.yml

@@ -44,6 +44,13 @@ jobs:
         with:
           python-version: '3.11'
 
+      - name: Install protobuf dependencies & generate proto files
+        uses: ./.github/actions/protobuf
+
+      - name: Install workspace packages
+        run: |
+          uv pip install --no-deps -e sdk/python -e api/v2alpha1/python -e kubernetes_platform/python -e backend/api/v2beta1/python_http_client
+
       - name: Create KFP cluster
         id: create-kfp-cluster
         uses: ./.github/actions/create-cluster

.github/workflows/readthedocs-builds.yml

@@ -24,9 +24,11 @@ jobs:
           python-version: "3.10"
           extra: docs
 
-      - name: Generate proto files and install packages
+      - name: Install protobuf dependencies & generate proto files
+        uses: ./.github/actions/protobuf
+
+      - name: Generate kfp-kubernetes proto files and install packages
         run: |
-          make -C api python
           make -C kubernetes_platform python
           uv pip install --no-deps -e sdk/python -e api/v2alpha1/python -e kubernetes_platform/python -e backend/api/v2beta1/python_http_client
 

components/test_load_all_components.sh

@@ -23,10 +23,8 @@
 
 cd "$(dirname "$0")"
 
-PYTHONPATH="$PYTHONPATH:../sdk/python"
-
 echo "Testing loading all components"
-find . -name component.yaml | python3 -c '
+find . -name component.yaml | uv run python -c '
 import sys
 import kfp