Fix doc-tools not found error in test-mcp-examples workflow

- Add npm install step to install @redpanda-data/docs-extensions-and-macros
- Use --no-install flag with npx to prevent trying to download from npm
- The doc-tools binary is provided by @redpanda-data/docs-extensions-and-macros

Author: JakeSCahill

.github/workflows/test-mcp-examples.yaml

@@ -28,8 +28,11 @@ jobs:
         with:
           node-version: '22'
 
-      - name: Install doc-tools and dependencies
-        run: npx doc-tools install-test-dependencies
+      - name: Install npm dependencies
+        run: npm install
+
+      - name: Install doc-tools dependencies
+        run: npx --no-install doc-tools install-test-dependencies
 
       - name: Make test script executable
         run: chmod +x modules/ai-agents/examples/test-mcp-examples.sh