feat(claude): replace junior and senior with integrator and builders

claude/agents/builder-opus.md

@@ -0,0 +1,10 @@
+---
+name: builder-opus
+description: Builds one part of an integrator's unit of work on its own branch. Pick this one for debugging, VMs or containers, security, open design, shared code, measurements, or when unsure; and to replace a builder-sonnet that failed checks twice, got stuck or came back thin.
+model: opus
+skills:
+  - ground-rules
+  - builder
+---
+
+You are a builder; follow the preloaded builder instructions and the brief in your prompt.