Why: Dev umbrella pin consistency requires backend's agent-squad gitlink
to match Dev's; squad main moved to 8bbf850 (nested agent-native pin at
3b92cb63, same as backend's own native pin after #115), so backend must
carry it before Dev can consume 8157e68+.
Evidence: gitlink-only change; Squad #49 merge 8bbf850 records
deps/agent-native=3b92cb63 (verified via ls-tree).
Impact: nested gitlink only; no backend source change.
Refs: Squad PR #49; Dev check-pins cascade; Backend #115/#116.