changeset: dated notes on the two pending entries the closed gap sets make false

`.changeset/6151-stack-schema-omit-collapse.md` read `gap` as one `number`
member declared once on `FlexLayoutProps`; `StackSchema` now declares its own
literal union over an `Omit` of it. `.changeset/11441-retire-nav-responsive-grid-layout.md`
said `grid` accepts a `gap` number; it now accepts one of ten steps. Each gets
an append-only dated note in the house form naming objectui#11474 and the
changeset that ships.

Claude-Session: https://claude.ai/code/session_01XvhGmGAP79ZB8swnkapxPC
Co-authored-by: Claude <noreply@anthropic.com>

Author: claude

.changeset/11441-retire-nav-responsive-grid-layout.md

@@ -15,3 +15,5 @@ Migration, measured against `objectui validate` on both of its faces:
 - `basePath` has no app-document spelling: the strict face refuses it as an unrecognized key. It belongs to the shell, as `AppSchemaRenderer`'s `basePath` prop.
 
 **Clause-②: yes** — two registrations leave the runtime (narrowing), released as `minor` with this banner.
+
+⚠️ **Dated note, 2026-10-02 — `grid` takes one of ten `gap` steps, not any number — objectui#11474.** At this change `grid` accepted any `gap` number; now it accepts one of 0, 1, 2, 3, 4, 5, 6, 8, 10 and 12, the steps the `grid` renderer maps, and `objectui validate` refuses any other `G` at `gap` on both faces with that set named: 7, 9, 11, a number above 12, a negative number or a fraction. For such a number `grid` drew no gap anyway, because the class it built at runtime is in no compiled stylesheet. So in the migration above `G` must be one of those ten steps; each step `ResponsiveGrid`'s own class map drew (0 to 6 and 8) is one of them. `.changeset/11474-layout-spacing-sets.md` states what ships. The rest of this entry is kept as the reading of this change.

.changeset/6151-stack-schema-omit-collapse.md

@@ -50,3 +50,17 @@ package's own tsconfig and asserts (1) `StackSchema` declares exactly what `Flex
 declares, and (2) no member of the `LayoutSchema` union has lost any of `BaseSchema`'s
 named members — so the next heritage clause that collapses under the index signature reds
 for the whole class, not just for this one interface.
+
+⚠️ **Dated note, 2026-10-02 — `StackSchema` declares its own `gap` — objectui#11474.**
+At this change `gap` was a `number` member of `FlexLayoutProps`, declared once and inherited by
+`FlexSchema` and `StackSchema` alike, and `stack.tsx` was read as feeding it to a Tailwind
+numeric scale; now each node's `gap` is the closed set of steps its renderer maps.
+`FlexLayoutProps.gap` is `0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8`, shared by `FlexSchema` and the
+authored `flex` bag. `StackSchema` extends `BaseSchema` and `Omit<FlexLayoutProps, 'gap'>` and
+declares its own `gap?: 0 | 1 | 2 | 3 | 4 | 5 | 6 | 8 | 10`, the nine steps `stack.tsx` has a
+gap class for. So `gap` is declared twice while the other members stay declared once, and `tsc`
+refuses any other number on a `stack`, as it refuses `gap: 'large'`. That `Omit` crosses no
+index signature (`FlexLayoutProps` carries none), so it erases no member name, and
+`stack-schema-emitted-members.test.ts`, which measures the emitted declaration, still passes.
+`.changeset/11474-layout-spacing-sets.md` states what ships. The rest of this entry is kept as
+the reading of this change.