cn commands: use omarchy-cmd helpers per bin style rule

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QKxGW1raAWaqeU8WdHsMsp

bin/omarchy-cn-ai-doctor

@@ -25,7 +25,7 @@ provider=$(cn_ai_profile_field "$profile" provider)
 command=$(cn_ai_harness_field "$harness" command)
 proto=$(cn_ai_harness_field "$harness" protocol)
 
-if command -v "$command" > /dev/null 2>&1; then
+if omarchy-cmd-present "$command"; then
   echo "PASS ai: harness $harness installed ($command)"
 else
   install=$(cn_ai_harness_field "$harness" install)