Why: PR #152 pinned the bundled core back to 7a98a7e citing "Dev core is
at 7a98a7e", but Dev origin/main pins modules/core at 89f3906; the
misalignment breaks Dev check-pins for any tree that materializes
recorded pointers (exposed by a fresh task worktree running make test).
Evidence: go build ./... and internal/server + internal/store tests
green on the repinned tree.
Impact: restores modules/backend/deps/agent-system-core == Dev
modules/core (89f3906), unblocking Dev gitlink bumps.
Refs: Dev task feature/admin-auth-gate-fix.
weichen