Add client-side validation for tool output schemas

- Cache tool output schemas when listing tools - Validate structuredContent against outputSchema during callTool - Enforce that tools with outputSchema must return structuredContent - Add json-schema-to-zod dependency for schema conversion - Add comprehensive tests for validation scenarios 🤖 Generated with [Claude Code](https://claude.ai/code) Co-Authored-By: Claude <noreply@anthropic.com>

Author: bhosmer-ant

package-lock.json

@@ -52,6 +52,7 @@
  "eventsource": "^3.0.2",
  "express": "^5.0.1",
  "express-rate-limit": "^7.5.0",
+ "json-schema-to-zod": "^2.6.1",
  "pkce-challenge": "^5.0.0",
  "raw-body": "^3.0.0",
  "zod": "^3.23.8",