Task 3's implementer independently hit and fixed this exact bug
(a vi.fn() given a zero-arg implementation, then invoked via a spread
of unknown[] args inside a vi.mock factory, fails tsc -b with TS2556).
Applied the same fix (explicit vi.fn<...> generic type) to the other
occurrences of this pattern still written the old way in this plan's
Task 3 and Task 4 sections, so those implementers don't have to
rediscover it from scratch. Task 5, 10, and 11's occurrences were
checked and found to already use safe patterns (single literal-arg
calls, or bare vi.fn() with no implementation) that don't trigger this.
Claude-Session: https://claude.ai/code/session_01NhxA4npAXAxmCDEJt6kxSH
063874b60c