feat(theme): add input-date recipe

.claude/skills/implement-recipe/SKILL.md

@@ -543,6 +543,40 @@ export const useSpinnerRecipe = createUseRecipe(
 );
 ```
 
+#### Spacing multipliers inside a `setup` callback — use `calc(@token * N)`
+
+Bare numeric spacing refs like `@0.125` / `@0.25` are **multiplier tokens** that
+resolve to a variable *named* `"0.125"`. In a recipe's `base` / `variants` these are
+auto-declared on the fly (e.g. spinner/badge size variants use `@0.25`, `@0.5`). But
+raw `selector(...)` calls inside a `setup` callback only **reference** — they do NOT
+auto-declare. Referencing `@0.125` in a setup selector throws at Storybook build init:
+`Variable "0.125" is not defined` (typecheck + theme tests do NOT catch this).
+
+To scale a token by a fraction inside a setup selector, use an **embedded reference
+expression wrapped in `calc()`** as a plain string:
+
+```ts
+(s) => {
+	const { selector } = s;
+	selector(".input-date-field", {
+		gap: "calc(@spacing * 0.125)", // → gap: calc(var(--spacing) * .125)
+	});
+}
+```
+
+Styleframe's resolver (`engine/core/src/tokens/resolve.ts`) treats an *exact* `@name`
+match as a validated reference (throws if undefined) but parses an *embedded* expression
+like `@spacing * 0.125` without validation — it resolves `@spacing` and keeps the rest
+literal. This is the same pattern used by dropdown/tooltip/popover (`"calc(@tooltip.arrow.size * -1)"`).
+
+- **Keep the arithmetic inside `calc(...)`.** Bare `"@spacing * 0.125"` parses but emits
+  invalid CSS `gap:var(--spacing) * .125` (no `calc` → the browser drops the declaration).
+- **Test gotcha:** in the recipe test instance, declare `s.variable("spacing", "1rem")` and
+  let the calc resolve — do NOT hand-declare a fake `s.variable("0.125", ...)`, which masks
+  the real build failure.
+- **Always run `pnpm --filter @styleframe/storybook build` during verification** — it is the
+  only check that exercises real token resolution in a fresh instance.
+
 ---
 
 ### Deliverable 2: Barrel index

.claude/skills/verify-recipe/SKILL.md

@@ -68,15 +68,25 @@ Parse output. Capture:
 - Exit status.
 - For each issue: file:line, rule, message.
 
-### Step 3: (Optional) Storybook spot-check
-
-If the user wants, offer to start Storybook briefly to verify the story renders:
+### Step 3: Storybook build (required)
 
 ```bash
-pnpm storybook
+pnpm --filter @styleframe/storybook build
 ```
 
-This is a manual check — the assistant cannot verify rendering automatically. Prompt the user to open the component story in the browser and confirm it looks correct.
+Run the **production build**, not just the dev server. This is the **only** check that
+exercises real token resolution in a fresh Styleframe instance — typecheck and theme
+tests pass even when a recipe references an undefined variable. A `setup` callback that
+references an undeclared spacing multiplier (e.g. a raw `selector` using `@0.125`) throws
+here with `Variable "0.125" is not defined`; the fix lives in `/implement-recipe` (use
+`calc(@spacing * 0.125)` instead — see that skill's Step 12). Capture exit status and any
+`Variable "..." is not defined` errors with the originating recipe file.
+
+#### (Optional) Storybook render spot-check
+
+If the user wants a visual check, offer to start Storybook (`pnpm storybook`) — but this is
+manual; the assistant cannot verify rendering automatically. Prompt the user to open the
+story and confirm it looks correct.
 
 ### Step 4: Write `verification.md`
 
@@ -115,7 +125,10 @@ Do NOT attempt to fix issues automatically.
 ## Lint: <pass | fail>
 <!-- If fail, list: file:line — rule — message — suggested sub-skill -->
 
-## Storybook spot-check: <pass | not run | manual-deferred>
+## Storybook build: <pass | fail>
+<!-- If fail, list: recipe file — "Variable ... is not defined" — suggested sub-skill (/implement-recipe) -->
+
+## Storybook render spot-check: <pass | not run | manual-deferred>
 
 ## Summary
 - Total failures: <N>
@@ -129,6 +142,7 @@ Do NOT attempt to fix issues automatically.
 - [ ] `pnpm typecheck` was run from the project root.
 - [ ] `pnpm --filter @styleframe/theme test` was run.
 - [ ] `pnpm lint` was run.
+- [ ] `pnpm --filter @styleframe/storybook build` was run (catches token-resolution errors).
 - [ ] Each failure is reported with file:line and a suggested sub-skill.
 - [ ] `verification.md` is written to `.context/recipe-<name>/`.
 - [ ] User received a short pass/fail summary.