feat: add DeepSeek and NVIDIA NIM providers

- Add deepseek and nvidia entries to gateway-provider config

- Add DEEPSEEK_API_KEY and NVIDIA_API_KEY to .env.example

- Add deepseek and nvidia to doctor's LLM provider check

- Fix remaining harness-log → log-message reference

lisp/security-validator.lisp

@@ -0,0 +1,13 @@
+(defun validator-protocol-check (msg)
+  "Enforces structural schema compliance on protocol messages."
+  (validate-communication-protocol-schema msg))
+
+(defskill :passepartout-security-validator
+  :priority 95
+  :trigger (lambda (ctx) (declare (ignore ctx)) t)
+  :deterministic (lambda (action ctx)
+                   (declare (ignore ctx))
+                   (handler-case
+                       (progn (validator-protocol-check action) action)
+                     (error (c)
+                       (list :type :LOG :payload (list :level :error :text (format nil "Protocol Violation: ~a" c)))))))