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/system-memory.lisp

@@ -0,0 +1,7 @@
+(defun memory-inspect ()
+  "Allows the system to inspect its own memory state."
+  (harness-log "MEMORY: Self-inspection triggered."))
+
+(defskill :passepartout-system-memory
+  :priority 100
+  :trigger (lambda (ctx) (declare (ignore ctx)) nil))