Replaces the original "useful to me, specifically" gate with "me OR a friend
returns unprompted in >=2 separate weeks" — friendly-user signal counts, but the
test stays behavioural (return usage) not feedback-based, to resist politeness
bias. Folds the old Stage 1 ("a trusted user returns") into the new Stage 0 (they
were near-identical), renumbers hardening to Stage 1, and updates the drift
signals (the gate can be softened by mistaking polite feedback for evidence;
multi-user shipping ahead of the gate was a recorded exception per ADR-012, not a
precedent). Rationale recorded in ADR-016.
The top-level guardrail for Tapir: the problem, the product, the principles
(local-first, standalone-first, attention-as-scarce-resource, data isolation),
who it's for (now / Future B / deferred Future C), and a staged, falsifiable
definition of success with Stage 0 ("useful to me") as the gate.
mathias