[2.0 / next] A first answer landing in the same tick as an action that writes its input stays behind Loading under latest() #4696

Ruled-not-built row S-45 (leaf and memo cases) from #4695. The ruling is in packages/web/test/async-gen/rulings/S-45.ts, and the generated block is in packages/signals/docs/SCENARIOS.md. Rules: D-22, F-9.

Shape: m0 = s0 + 1 is async and still on its first load. The first answer and an action that writes s0 land in the same tick. A <Loading> reads only latest(m0), directly in the leaf case and through a sync memo in the memo case.

Ruled: once the answer lands (step 4), the screen is vs0:0 lm0:1. latest returns the answer (D-22), and the plain s0 read stays committed.

Today: the Loading keeps its fallback (vs0:0 [L]), waiting on an action it never read (see S-40). The through-a-memo form was documented as standing, but it also shows the fallback.

The rows are it.fails in rulings.spec.ts. Flip them to it when this is fixed.