fix: agent template mappings + roundtable sections injection

Critical: Peter was missing design_review — spawned tasks would go unclaimed.
All 4 agents now have design_roundtable in supported_templates.
Removed design_polish from Peter (Elena does polish, not Peter).
Added sections block to design_roundtable for deliverables/RAG access.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

templates/design_roundtable.yml

@@ -12,6 +12,14 @@ participants:
 iteration_limit: 3
 convergence_signal: "CONSENSUS REACHED"
 
+sections:
+  - agent
+  - project
+  - rag
+  - deliverables
+  - message
+  - instructions
+
 steps:
   - type: boardroom
     loop: