fix(carousel,galleria,timeline): enable generic type inference for value and slots

[YevheniiKotyrlo]

Defect Fixes

Fixes #8487

Carousel, Galleria, and Timeline use any for their value arrays and slot scoped data. Developers get no IDE autocomplete and no compile-time safety when rendering items in these data-display components.

Same root cause as #8442 — DefineComponent's no-arg constructor prevents generic inference. Same fix pattern as #8444 (DataTable/DatePicker).

Related: #7426, #6041

Reproducer: StackBlitz — bun run type-check (0 errors, typo undetected) → bun run patch && bun run type-check (TS2339 catches it)

Problem

<Carousel :value="products">
  <template #item="{ data }">
    {{ data.naem }}
    <!-- No error — `data` is `any`, typo ships to production -->
  </template>
</Carousel>

After this fix, TypeScript infers T from the :value binding and flows it to all slots:

<Carousel :value="products">
  <template #item="{ data }">
    {{ data.naem }}
    <!-- TS2339: Property 'naem' does not exist on type 'Product' -->
  </template>
</Carousel>

Changes

For each component:

• [Component]Props<T = any> — value: T[]
• [Component]Slots<T = any> — all data-bearing slot parameters become T
• Generic constructor: new <T = any>(props: [Component]Props<T>) with $slots: [Component]Slots<T>

What gets typed

Slot	Before	After
Carousel #item data	any	T
Galleria #item / #caption / #thumbnail item	any	T
Timeline #content / #opposite / #marker / #connector item	any	T

Scope / Impact

• No breaking changes — backward compatible, T defaults to any
• No runtime changes — types only (.d.ts files)
• 3 components: Carousel, Galleria, Timeline

Verification

Gate	Result
pnpm run format:check	PASS
pnpm run lint	PASS
pnpm run test:unit	Pre-existing failures only, 0 new
pnpm run build:packages	PASS

Series

This is part of a series bringing generic type inference to all PrimeVue data components:

PR	Components	Status
#8444	DataTable, DatePicker	Open
#8484	Select, MultiSelect, Listbox	Open
#8485	Column (phantom of prop)	Open
#8489	AutoComplete, CascadeSelect, DataView	Open
#8490	Carousel, Galleria, Timeline	This PR
#8491	OrderList, PickList	Open
#8493	VirtualScroller, SelectButton, InputChips	Open

After this series, every PrimeVue component with a collection prop will infer T from the binding and flow it to slots — giving developers full IDE autocomplete and compile-time type safety in templates.