ground-truth-gates: a gate over hardcoded facts asserts the facts, not just the shape

[firaen22]

What

New rule 6 under "What makes a gate real". When code embeds domain constants (holiday dates, a tax rate, a fee schedule, a valid-state set), a structure-only suite passes identically whether the values are right or a later edit corrupted one. Those values were usually cross-checked once — but in the conversation, which evaporates at session end. Anchor the load-bearing values as assertions from the authority you already consulted, so a future silent constant change fails.

Why

This extends item 2's carve-out — from an output-interface string to an embedded input constant — and is distinct from item 3's "hardcoded expected value" fake-pass: the anchor's value comes from an external authority, not copied back from the code's own output. Item 3's tautology asserts the source is the source; this asserts the source matches the world.

Class-distilled from a mining pass over the owner's own sessions (no code taken): a "tests check shape, not date-truth" cross-model finding on hardcoded holiday dates that had been cross-checked against four sources — but only in chat, never in the gate.

Ships unprobed per the covenant. .github/checks.py green.

Revision note (2026-07-24)

Force-pushed after a same-day adversarial self-audit found the original "Why" over-claimed: it said this rule "IS item 2's carve-out used correctly," but item 2's carve-out is explicitly scoped to output-interface contracts with downstream consumers (an error-message string, an output name) — a holiday date is an embedded input constant, not an interface. Reframed as an extension of that carve-out rather than a direct instance of it, and added the reconciliation with item 3's "hardcoded expected value" fake-pass (left unaddressed in the original draft) — the two are distinguished by the expected value's provenance, not its presence.

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