refactor(ci): Optimize workflows and secure JSON passing

1. Enable caching for `setup-uv` in `continuous-integration.yml` and
   `release-publish.yml` to speed up CI runs.
2. Secure JSON passing in `discussion_answering.yml` by using an environment
   variable instead of writing it via inline bash heredoc to prevent potential
   script injection.

Co-authored-by: Shangjie Chen <deanchen@google.com>
PiperOrigin-RevId: 940546688

Author: DeanChensj

.github/workflows/continuous-integration.yml

@@ -67,6 +67,8 @@ jobs:
 
       - name: Install uv
         uses: astral-sh/setup-uv@v7
+        with:
+          enable-cache: true
 
       - name: Generate Baseline
         env:
@@ -134,6 +136,8 @@ jobs:
 
       - name: Install the latest version of uv
         uses: astral-sh/setup-uv@v7
+        with:
+          enable-cache: true
 
       - name: Install dependencies
         run: |

.github/workflows/discussion_answering.yml

@@ -65,9 +65,7 @@ jobs:
           REPO: 'adk-python'
           INTERACTIVE: 0
           PYTHONPATH: contributing/samples/adk_team
+          DISCUSSION_JSON: ${{ toJson(github.event.discussion) }}
         run: |
-          # Write discussion data to temporary file to avoid secret masking issues
-          cat > /tmp/discussion.json << 'EOF'
-          ${{ toJson(github.event.discussion) }}
-          EOF
+          python -c "import os; open('/tmp/discussion.json', 'w').write(os.environ['DISCUSSION_JSON'])"
           python -m adk_answering_agent.main --discussion-file /tmp/discussion.json

.github/workflows/release-publish.yml

@@ -70,6 +70,7 @@ jobs:
         uses: astral-sh/setup-uv@v7
         with:
           version: "latest"
+          enable-cache: true
 
       - name: Set up Python
         uses: actions/setup-python@v6