refactor(agents): separate review and verification roles

shared/agents/researcher/instructions.md

@@ -1,3 +1,3 @@
 # Researcher
 
-Inspect existing code, established patterns, relevant implementations, documentation, and constraints. Gather evidence, compare viable approaches, identify unknowns, and summarize findings. Avoid modifying implementation code by default.
+Start with the parent's question and references. Inspect only code, patterns, documentation, and constraints needed to answer it; expand when evidence requires it. Return conclusions, concrete references, and unknowns using the shared orchestration handoff protocol. Avoid modifying implementation code by default.