feat(Board): widget selection and rigid group movement

.changeset/board-selection-and-group-move.md

@@ -0,0 +1,55 @@
+---
+'@cube-dev/ui-kit': minor
+---
+
+Add widget selection and rigid group movement to `Board`.
+
+Set `selectionMode="single" | "multiple"` and read the selection with
+`selectedKeys` / `defaultSelectedKeys` / `onSelectionChange` (keys are layout item
+ids, always returned in layout order).
+
+Pressing a widget selects it on pointer-down and arms a drag of the selection —
+selecting and grabbing are one gesture, so move the pointer and it drags, stay
+still and it was only a selection. <kbd>Shift</kbd> (or <kbd>Cmd</kbd>/
+<kbd>Ctrl</kbd>) toggles membership, dragging from empty canvas lassos
+(`allowMarqueeSelection`), <kbd>Space</kbd> toggles the focused widget, and
+<kbd>Escape</kbd> clears.
+
+Selection behaves like focus: it tracks what the user is working with and moves on
+as soon as they touch something else — pressing another widget makes that the
+selection, and pressing an interactive control inside a widget or moving focus off
+the board drops it entirely.
+
+With `"multiple"`, dragging any selected widget moves the whole selection as a
+rigid block that reflows by the board's own rules — the same compaction a single
+widget gets, so a group can never be parked in empty space on a `vertical` board
+and the widgets around it close the gap in the same frame. Every widget travels by the same delta, the group clamps against the
+grid edge as a unit instead of collapsing into it, a frame that cannot be placed
+is rejected outright rather than partially applied, and the move commits through a
+single `onLayoutChange`. Arrow keys move the group too. `BoardInteractionInfo`
+gains `items`, `oldItems` and `placeholders` describing the whole gesture; the
+existing `item` / `oldItem` / `placeholder` fields are unchanged, and a board with
+no selection behaves exactly as before.
+
+The `selectionCancel` selector (board- or widget-level, defaulting to the exported
+`BOARD_SELECTION_CANCEL`) marks interactive descendants; `[data-no-select]` opts
+out a custom control. On a selectable board it also gates dragging, which fixes a
+long-standing trap: `useMove`'s pointer-down calls `preventDefault()`, so without
+a `dragCancel` an `input` inside a widget could not be focused or typed into.
+Selected widgets are drawn with a `#primary-border` border and a `#primary` ring —
+an edge treatment rather than a fill, since selection reads as a focus-like state;
+`outline` stays reserved for the real focus ring. Widgets get a `selected`
+modifier you can restyle through `widgetProps.styles`.
+
+`onWidgetsDelete` reports a <kbd>Delete</kbd>/<kbd>Backspace</kbd> press with a
+non-empty selection. Board never mutates the layout itself, so removal stays
+yours to implement and to make undoable.
+
+Accessibility: widget hosts are now `role="group"` with an accessible name from
+the new `Board.Widget` `aria-label` prop (falling back to `qa`, then the layout
+id). `aria-roledescription` is now localized rather than hardcoded English — it
+was previously also invalid, sitting on a role-less element. Selected widgets are
+described as "Selected", and selection changes are announced through a polite live
+region.
+
+Widget hosts also expose `data-board-widget-id` and `data-selected`.

.size-limit.cjs

@@ -20,15 +20,20 @@ module.exports = [
         }),
       );
     },
-    // 460.16 kB at the time of writing. Raised from 460 kB for Tasty v3, which
-    // it exceeded by 161 B — its new dev diagnostics ship in every bundle,
-    // because `isDevEnv()` is evaluated at runtime so one build serves dev and
-    // production. Headroom is deliberately small so real bloat still trips the
-    // budget.
+    // 464.27 kB at the time of writing. Raised from 462 kB for Board selection
+    // and group movement: ~3.5 kB of engine (a rigid multi-item move primitive,
+    // selection state, marquee hit-testing, a live region) plus ~0.5 kB for the
+    // six `board.*` strings across twelve locales, which are all registered
+    // eagerly. Measured by building with and without the locale keys.
+    //
+    // The Button budget below is unchanged, which is the check that matters:
+    // none of this reaches a consumer who does not import `Board`.
+    //
+    // Headroom is deliberately small so real bloat still trips the budget.
     //
     // Note when checking locally: `size-limit` bundles the built `./dist`, it
     // does not build. Run `pnpm build` first or you will measure a stale bundle.
-    limit: '462kB',
+    limit: '466kB',
   },
   {
     name: 'Tree shaking (just a Button)',

AGENTS.md

@@ -117,6 +117,28 @@ See `src/stories/CreateComponent.docs.mdx` (Storybook → **Getting Started / Cr
 
 See `src/stories/Usage.docs.mdx` (Storybook → **Getting Started / Usage**) for units, base/spacing/size/shadow/layout tokens, color tokens, typography presets, themes, recipes, modifiers, state syntax, icons, and the form system.
 
+## i18n
+
+Full rules in [`src/i18n/README.md`](src/i18n/README.md). The short version:
+
+- **Scope: strings a component renders.** Anything the component itself puts in
+  front of a user — visible text, `aria-label`, `aria-roledescription`, live-region
+  announcements, `title` — goes through `useI18n()`:
+  `t('component.key', 'English default')`. The inline English stays as a
+  belt-and-braces fallback.
+- **Not for stories, docs, or tests.** Storybook stories, `.docs.mdx`, and specs are
+  demo and fixture copy, not product UI. Use plain literals there — a locale key
+  that exists only to feed a story is noise in twelve files, and a test that reads
+  its expectation from the bundle asserts nothing about the string.
+- **Component props that expose a label stay overrides** that win over the
+  translated default: `emptyLabel = t('...', 'No items')`.
+- **All 12 locales, every time.** `en-US` is the source of truth;
+  `locale-parity.test.ts` fails CI if any locale's key set or `{{interpolation}}`
+  tokens diverge. Interpolation is `{{double}}` braces with no ICU, so plurals need
+  separate keys rather than a plural rule.
+- **If a string doubles as a DOM selector**, build the selector from the same
+  `t(...)` value so the two cannot drift when the language changes.
+
 ## TypeScript & Exports
 
 - **Module augmentation:** `src/tasty-augment.d.ts` extends `@tenphi/tasty` with project-specific color tokens, preset names, and theme names.