fix(createSelection,createGroup): batch onboard to prevent N cache invalidations

Composables that override register() but not onboard() had two bugs:
1. Inherited onboard called base register via closure, skipping custom logic
2. No batch wrapping caused N cache invalidations + N event dispatches

Add batched onboard overrides to createSelection, createGroup, createNested,
useFeatures, createQueue, and useTheme. Post-batch mandate() call handles
mandatory force mode where seek() needs fresh cache.

Author: johnleider

packages/0/src/composables/createGroup/index.ts

@@ -289,7 +289,9 @@ export function createGroup<
   }
 
   function onboard (registrations: Partial<Z>[]): E[] {
-    return registrations.map(registration => register(registration))
+    const tickets = selection.batch(() => registrations.map(registration => register(registration)))
+    if (toValue(mandatory) === 'force') selection.mandate()
+    return tickets
   }
 
   function reset () {

packages/0/src/composables/createNested/index.ts

@@ -587,7 +587,7 @@ export function createNested<
   }
 
   function onboard (registrations: NestedRegistration<Z>[]): E[] {
-    return registrations.map(registration => register(registration))
+    return group.batch(() => registrations.map(registration => register(registration)))
   }
 
   function clear (): void {

packages/0/src/composables/createQueue/index.ts

@@ -416,10 +416,15 @@ export function createQueue<
 
   onScopeDispose(dispose, true)
 
+  function onboard (registrations: Partial<Z>[]): E[] {
+    return registry.batch(() => registrations.map(registration => register(registration)))
+  }
+
   return {
     ...registry,
     register,
     unregister,
+    onboard,
     offboard,
     pause,
     resume,

packages/0/src/composables/createSelection/index.ts

@@ -307,7 +307,9 @@ export function createSelection<
   }
 
   function onboard (registrations: Partial<Z>[]): E[] {
-    return registrations.map(registration => register(registration))
+    const tickets = registry.batch(() => registrations.map(registration => register(registration)))
+    if (toValue(mandatory) === 'force') mandate()
+    return tickets
   }
 
   function reset () {

packages/0/src/composables/useFeatures/index.ts

@@ -185,10 +185,15 @@ export function createFeatures<
     }
   }
 
+  function onboard (registrations: Partial<Z>[]): E[] {
+    return registry.batch(() => registrations.map(registration => register(registration)))
+  }
+
   return {
     ...registry,
     variation,
     register,
+    onboard,
     sync,
     get size () {
       return registry.size

packages/0/src/composables/useTheme/index.ts

@@ -294,11 +294,16 @@ export function createTheme<
     return registry.register(item as unknown as Partial<SingleTicketInput<ThemeColors>>) as unknown as E
   }
 
+  function onboard (registrations: Partial<Z>[]): E[] {
+    return registry.batch(() => registrations.map(registration => register(registration)))
+  }
+
   return {
     ...registry,
     colors,
     isDark,
     register,
+    onboard,
     cycle,
     get size () {
       return registry.size

skills/vuetify0/SKILL.md

@@ -140,6 +140,31 @@ const theme = inject('theme') // Could be undefined!
 const [useTheme, provideTheme] = createContext<ThemeContext>('Theme')
 ```
 
+### ❌ Don't override `register` without overriding `onboard`
+```ts
+// Bad — inherited onboard calls base register via closure, skipping your logic
+function register (item) {
+  const ticket = registry.register({ ...defaults, ...item })
+  doCustomStuff(ticket)
+  return ticket
+}
+return { ...registry, register } // onboard still calls base register!
+```
+
+### ✅ Always pair custom `register` with batched `onboard`
+```ts
+// Good — onboard routes through your register and batches cache/events
+function register (item) {
+  const ticket = registry.register({ ...defaults, ...item })
+  doCustomStuff(ticket)
+  return ticket
+}
+function onboard (items) {
+  return registry.batch(() => items.map(item => register(item)))
+}
+return { ...registry, register, onboard }
+```
+
 ### ❌ Don't write SSR checks manually
 ```ts
 // Bad