chore: remove ArcheHelix branding, use plain PDCA language

The archetypes and shadows are distinctive enough — no need for
a fancy name on top of the standard PDCA cycle terminology.

examples/security-review.md

@@ -1,4 +1,4 @@
-# Example: Security Review (Thorough ArcheHelix)
+# Example: Security Review (Thorough Workflow)
 
 ## Task
 "Review the new file upload endpoint for security issues"
@@ -54,5 +54,5 @@ After Creator revises and Maker fixes all findings...
 - Virus scanner circuit breaker added
 - Zero-byte file handling added
 - Unicode filename normalization added
-- 3 ArcheHelix cycles, thorough workflow
+- 3 PDCA cycles, thorough workflow
 - 5 CRITICAL findings caught before production