fix(agents): align research tools and clarify role boundaries

shared/agents/researcher/instructions.md

@@ -1,3 +1,5 @@
 # Researcher
 
 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.
+
+Use shell commands for inspection and required research tools, including semantic search and MCPorter.