feat: add TypeScript declarations for @juspay-tech/react-hyper-js

[ArushKapoorJuspay]

Summary

• Creates src/index.d.ts (435 lines) with complete TypeScript declarations for all exported components, hooks, and types
• Adds compile-time type test file (src/index.test-d.ts, 370+ lines, 24 test categories) verified by tsc --noEmit
• Updates package.json with types and exports fields for proper TypeScript resolution

Changes

Provider Components (3)

• HyperElements — main SDK provider (accepts hyper: Promise<HyperInstance>)
• Elements — Stripe-compatible alias (accepts stripe prop)
• HyperManagementElements — saved payment method management provider

Element Components (12 + 5 aliases)

• PaymentElement / UnifiedCheckout
• CardElement / CardWidget
• CardNumberElement / CardNumberWidget
• CardExpiryElement / CardExpiryWidget
• CardCVCElement / CardCVCWidget
• ExpressCheckoutElement
• PaymentMethodsManagementElement

Hooks (5)

• useHyper() → UseHyperReturn (8 SDK methods + clientSecret)
• useWidgets() → UseWidgetsReturn (widget management)
• useElements() → Stripe-compatible alias
• useHyperSession() → HyperSession (self-contained session)
• useHyperElements() → HyperElementsContextType

Types (12+)

• UseHyperReturn, UseWidgetsReturn, HyperSession, SessionStatus
• HyperElementsProps, ElementsProps, PaymentElementComponentProps
• PaymentElementSessionProps, HyperElementsContextType
• All component prop interfaces with JSDoc documentation

Package.json Updates

• Added "types": "src/index.d.ts" field
• Added "exports" block with types condition
• Added typescript and @juspay-tech/hyper-js as devDependencies

Architecture Decision: Bare Exports

Uses bare export statements (NOT declare module "@juspay-tech/react-hyper-js") because:

1. The package uses main: "dist/bundle.js" — TypeScript resolves via types field
2. Bare exports work correctly with moduleResolution: "bundler" and "node16"
3. Matches the pattern used by similar React wrapper packages

Testing

npx tsc --project tsconfig.test.json --noEmit  # 0 errors

Related PRs

• juspay/hyper-js#18 — TypeScript declarations for core SDK
• juspay/hyperswitch-web — Demo app converted to TypeScript