Why: backend main pinned core 019617e (unfetchable post-migration) and the
store List* functions returned nil slices that encode as JSON null, which
crashed the frontend nav with .map on null (the 2026-09-30 white-screen).
Evidence: go test ./... across all packages; store regression
TestEmptyListsSerializeAsEmptyArrays asserts [] for empty project lists.
Impact: all 17 store list sites now initialize empty slices; build-blocker
core pin resolved; frontend no longer receives null for empty lists.
Refs: documents/records/2026-09-30-history-migration.md
weichen
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