Extract Implementer clarification into handoff guidance

packages/implementer-handoff/handoff.md

@@ -1,5 +1,11 @@
 # Handoff guide
 
+## Implementation and clarification
+
+Read the relevant files and make focused changes. Use the assigned investigation method for repository discovery; this handoff method owns clarification and report preparation.
+
+Ask the planner for more information when blocked after reasonable investigation. If the final contract appears wrong, explain the mismatch clearly, make the safest local correction if obvious within the authoritative scope, and validate it. Clarification methods guide communication; scope changes require owner authority.
+
 ## Documentation
 
 - Update the current-behavior contract only for behavior verified on the candidate. Keep proposed work clearly proposed.