chore(workflows): switch default Opus pin to opus[1m] alias

.archon/workflows/defaults/archon-adversarial-dev.yaml

@@ -117,7 +117,7 @@ nodes:
   - id: adversarial-sprint
     depends_on: [init-workspace]
     idle_timeout: 600000
-    model: claude-opus-4-6[1m]
+    model: opus[1m]
     loop:
       prompt: |
         # Adversarial Development — Sprint Loop

.archon/workflows/defaults/archon-feature-development.yaml

@@ -8,7 +8,7 @@ description: |
 nodes:
   - id: implement
     command: archon-implement
-    model: claude-opus-4-6[1m]
+    model: opus[1m]
 
   - id: create-pr
     command: archon-create-pr

.archon/workflows/defaults/archon-fix-github-issue.yaml

@@ -133,7 +133,7 @@ nodes:
     command: archon-fix-issue
     depends_on: [bridge-artifacts]
     context: fresh
-    model: claude-opus-4-6[1m]
+    model: opus[1m]
 
   # ═══════════════════════════════════════════════════════════════
   # PHASE 5: VALIDATE

.archon/workflows/defaults/archon-idea-to-pr.yaml

@@ -52,7 +52,7 @@ nodes:
     command: archon-implement-tasks
     depends_on: [confirm-plan]
     context: fresh
-    model: claude-opus-4-6[1m]
+    model: opus[1m]
 
   # ═══════════════════════════════════════════════════════════════════
   # PHASE 4: VALIDATE

.archon/workflows/defaults/archon-piv-loop.yaml

@@ -415,7 +415,7 @@ nodes:
   - id: implement
     depends_on: [implement-setup]
     idle_timeout: 600000
-    model: claude-opus-4-6[1m]
+    model: opus[1m]
     loop:
       prompt: |
         # PIV Loop — Implementation Agent

.archon/workflows/defaults/archon-plan-to-pr.yaml

@@ -42,7 +42,7 @@ nodes:
     command: archon-implement-tasks
     depends_on: [confirm-plan]
     context: fresh
-    model: claude-opus-4-6[1m]
+    model: opus[1m]
 
   # ═══════════════════════════════════════════════════════════════════
   # PHASE 4: VALIDATE

.archon/workflows/defaults/archon-ralph-dag.yaml

@@ -189,7 +189,7 @@ nodes:
   - id: implement
     depends_on: [validate-prd]
     idle_timeout: 600000
-    model: claude-opus-4-6[1m]
+    model: opus[1m]
     loop:
       prompt: |
         # Ralph Agent — Autonomous Story Implementation

.archon/workflows/defaults/archon-refactor-safely.yaml

@@ -207,7 +207,7 @@ nodes:
   # ═══════════════════════════════════════════════════════════════
 
   - id: execute-refactor
-    model: claude-opus-4-6[1m]
+    model: opus[1m]
     prompt: |
       You are executing a refactoring plan with strict safety guardrails.