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>

agents/david/agent.yml

@@ -6,8 +6,9 @@ manages:
   - specialists
 supported_templates:
   - company_design
-  - bootstrap_company
   - design_review
+  - design_roundtable
+  - bootstrap_company
 character:
   professional_title: "Chief Technology Officer"
   alignment_professional: "methodical and infrastructure-obsessed"