fix: upgrade deprecated GitHub Actions to v4/v5 and fix MCP test job

actions/upload-artifact@v3 is fully deprecated and causes instant CI
failure. Also upgrades checkout, setup-python, cache, github-script,
and codecov actions to their latest major versions to resolve Node.js 20
deprecation warnings. Adds missing pytest install to MCP Vector DB test
job and pins ruff>=0.15 in CI to match local tooling.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/workflows/vector-db-export.yml

@@ -36,12 +36,12 @@ jobs:
       CONFIG_PATH_INPUT: ${{ github.event.inputs.config_path }}
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
       with:
         submodules: recursive
 
     - name: Set up Python 3.12
-      uses: actions/setup-python@v4
+      uses: actions/setup-python@v5
       with:
         python-version: '3.12'
 
@@ -144,7 +144,7 @@ jobs:
 
     - name: Upload vector database exports
       if: steps.check_config.outputs.exists == 'true'
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
         name: ${{ env.SKILL_NAME }}-vector-exports
         path: |
@@ -153,7 +153,7 @@ jobs:
 
     - name: Upload quality report
       if: steps.check_config.outputs.exists == 'true'
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
         name: ${{ env.SKILL_NAME }}-quality-report
         path: quality_report_${{ env.SKILL_NAME }}.txt