fix: export missing Vue component prop types

[velocitysystems]

Summary

• Add missing export keyword to ChapterTitleProps in src/elements/define/chapter-title-element.ts
• Re-export ChapterTitleProps, MediaLayoutProps, and SpinnerProps from src/exports/components.ts

These three types are imported by the generated vue.d.ts from './index', but were never exported from the public barrel. This silently breaks the entire declare module 'vue' augmentation, causing all vidstack custom elements to be unrecognized in Vue templates.

Fixes #1759

Test plan

• Create a Vue + TypeScript project with skipLibCheck: false and strictTemplates: true
• Import vidstack/vue types and use vidstack custom elements in a template
• Run npx vue-tsc --noEmit and confirm no missing export or TS2339 errors