docs(spec): teach DatasetMeasureSchema.format what a date measure can say

.changeset/dataset-measure-format-date-styles.md

@@ -0,0 +1,13 @@
+---
+"@objectstack/spec": patch
+---
+
+`DatasetMeasureSchema.format` now documents what a DATE-valued measure can and cannot say, and the numeral-pattern examples no longer stand as the whole story.
+
+The field was silent about date measures while advertising `e.g. "$0,0.00", "0.0%"` — the pattern grammar a date measure is precisely unable to read. An author with a `min` / `max` over a date field read that line, wrote `format: 'YYYY-MM-DD'`, parsed clean, and got the locale default.
+
+The statement is carried by a `.describe()` where there was none, so it reaches the published surfaces an author actually reads: the generated JSON Schema (`json-schema/ui/Dataset.json`, `DatasetMeasure.json`) and the reference table in `content/docs/references/ui/dataset.mdx`, whose Description cell for `format` had been rendering the silence as a blank. The docblock above it carries the longer measured record.
+
+What it now says, measured rather than assumed against the objectui pin this repo builds against: a numeral pattern applies to a numeric measure; a date-valued measure never reads a date PATTERN — a date-only value reads `format` as a display STYLE (`short`, `relative`), and a datetime value ignores `format` altogether.
+
+Nothing accepts or rejects differently: `format` remains `z.string().optional()` and no measure is refused. Documentation over a published schema (objectui#7178 ruled A).

content/docs/references/ui/dataset.mdx

@@ -84,7 +84,7 @@ const result = DatasetSchema.parse(data);
 | **aggregate** | `Enum<'count' \| 'sum' \| 'avg' \| 'min' \| 'max' \| 'count_distinct'>` | optional | Aggregation (sum/avg/count/...); omit when `derived` is set |
 | **field** | `string` | optional | Aggregated field; optional for count(*) |
 | **filter** | `any` | optional |  |
-| **format** | `string` | optional |  |
+| **format** | `string` | optional | Numeral pattern for a NUMERIC measure — grouping, decimals, percent; e.g. "0,0.00", "0.0%". An amount takes its symbol from `currency`, not from a "$" in the pattern. A DATE-valued measure never reads a date pattern: `"YYYY-MM-DD"` renders the locale default. A date-only value reads `format` as a display style (`short`, `relative`); a datetime value ignores it. |
 | **currency** | `string` | optional | Display currency code (ISO 4217) |
 | **derived** | `{ op: Enum<'ratio' \| 'sum' \| 'difference' \| 'product'>; of: string[] }` | optional |  |
 
@@ -125,7 +125,7 @@ const result = DatasetSchema.parse(data);
 | **aggregate** | `Enum<'count' \| 'sum' \| 'avg' \| 'min' \| 'max' \| 'count_distinct'>` | optional | Aggregation (sum/avg/count/...); omit when `derived` is set |
 | **field** | `string` | optional | Aggregated field; optional for count(*) |
 | **filter** | `any` | optional |  |
-| **format** | `string` | optional |  |
+| **format** | `string` | optional | Numeral pattern for a NUMERIC measure — grouping, decimals, percent; e.g. "0,0.00", "0.0%". An amount takes its symbol from `currency`, not from a "$" in the pattern. A DATE-valued measure never reads a date pattern: `"YYYY-MM-DD"` renders the locale default. A date-only value reads `format` as a display style (`short`, `relative`); a datetime value ignores it. |
 | **currency** | `string` | optional | Display currency code (ISO 4217) |
 | **derived** | `{ op: Enum<'ratio' \| 'sum' \| 'difference' \| 'product'>; of: string[] }` | optional |  |
 

packages/spec/src/ui/dataset.zod.ts

@@ -188,8 +188,39 @@ export const DatasetMeasureSchema = lazySchema(() => strictObject({
   field: z.string().optional().describe('Aggregated field; optional for count(*)'),
   /** Measure-scoped filter (e.g. only won deals for "won_amount"). */
   filter: FilterConditionSchema.optional(),
-  /** Display format, e.g. "$0,0.00", "0.0%". */
-  format: z.string().optional(),
+  /**
+   * Display format — a NUMERAL pattern controlling grouping, decimals and
+   * percent: `"0,0.00"`, `"0.0%"`. A `$` in the pattern is still honoured as a
+   * legacy literal, but a real amount takes its symbol from `currency` below,
+   * never from the pattern — see that field's note.
+   *
+   * A DATE-valued measure (`min` / `max` over a date field) never reads a date
+   * PATTERN here: `"YYYY-MM-DD"` is accepted by this schema, reaches the
+   * renderer, and produces the locale default. The shared date path takes a
+   * named STYLE instead, so a date-only value reads `format` as `short`
+   * (`Jul 4, '24`) or `relative` (`3 days ago` inside a ±7-day window, the
+   * absolute locale form outside it) — the same two words `DateCellRenderer`
+   * honours from `field.format` — while a DATETIME value ignores `format`
+   * altogether.
+   *
+   * Measured at the pin this repo builds against (`.objectui-sha` =
+   * `a472b0716`; re-derived at that pin 2026-09-07) in objectui
+   * `packages/core/src/utils/dataset-format.ts`: `formatMeasure` routes a
+   * non-numeric value through `formatMeasureDate` (`:184-197`), whose
+   * date-only arm threads `format` into the STYLE parameter of `formatDate`
+   * (`utils/date-display.ts:104-137`, whose `relative` branch falls back to
+   * the absolute form beyond ±7 days at `:90`), while its datetime arm calls
+   * `formatDateTime(v, { locale })` with no style at all (`:194`). Teaching
+   * the shared path a pattern grammar would change every list cell that reads
+   * it, so the gap is DOCUMENTED here rather than closed (objectui#7178 ruled
+   * A; the datetime half is objectui#7443).
+   */
+  format: z.string().optional().describe(
+    'Numeral pattern for a NUMERIC measure — grouping, decimals, percent; e.g. "0,0.00", "0.0%". '
+    + 'An amount takes its symbol from `currency`, not from a "$" in the pattern. A DATE-valued '
+    + 'measure never reads a date pattern: `"YYYY-MM-DD"` renders the locale default. A date-only '
+    + 'value reads `format` as a display style (`short`, `relative`); a datetime value ignores it.',
+  ),
   /**
    * Display currency (ISO 4217, e.g. "USD", "CNY"). Carried onto the result
    * field so presentations render a locale-correct symbol via `Intl` rather