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/custom-workflow.yaml

@@ -4,8 +4,8 @@
 name: api-design
 description: "API-first workflow with contract validation and adversarial testing"
 
-# The ArcheHelix configuration
-archehelix:
+# PDCA workflow configuration
+pdca:
   plan:
     archetypes: [explorer, creator]
     parallel: false  # sequential: Explorer feeds Creator

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

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