Why: Dev-level pin consistency (check-pins hard-errors on nested drift);
squad main advanced to 819b0c5 (a2a adapter module #47, StepSpec.Brief #46,
nested agent-native pin #48).
Evidence: full backend suite green against 819b0c5 (SELF); CI authoritative
(GATE).
Impact: nested deps/agent-squad 633e853 -> 819b0c5; no backend source
changes (backend consumes squad via wfcompile/squadadapter surfaces which
are unchanged since #99-#102).
Refs: Q3 plan WP4/WP6; Dev card .task/feature-agent-stack-q3.md