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/feature-implementation.md

@@ -1,4 +1,4 @@
-# Example: Feature Implementation (Standard ArcheHelix)
+# Example: Feature Implementation (Standard Workflow)
 
 ## Task
 "Add rate limiting to the API authentication endpoint"
@@ -41,4 +41,4 @@
 - 8 tests added (including real Redis failure simulation)
 - Rate limiting active on 3 auth routes
 - Documentation updated
-- 2 ArcheHelix cycles, standard workflow
+- 2 PDCA cycles, standard workflow