feat: integrate Zod schemas for opt-in runtime validation

[benminer]

Wires the auto-generated Zod schemas (from #124) into the SDK's resource layer for opt-in runtime validation.

Usage

const client = new Scope3Client({
  apiKey: 'sk_xxx',
  persona: 'buyer',
  validate: true,       // validate both inputs and responses
  // validate: 'input'  // validate request bodies only
  // validate: 'response' // validate API responses only
});

When enabled, invalid inputs throw Scope3ApiError(400) and unexpected API response shapes throw Scope3ApiError(502) with structured Zod validation details.

Default is off — zero overhead for existing consumers.

Changes

• src/validation.ts — Thin validation utility (validateInput, validateResponse, mode helpers)
• src/schemas/registry.ts — Hand-maintained mapping from resource operations to auto-generated Zod schemas
• src/types/index.ts — Add validate option to Scope3ClientConfig
• src/adapters/base.ts — Add validate to BaseAdapter interface
• src/adapters/rest.ts, src/adapters/mcp.ts — Thread validate config through adapters
• Resource files — Wire validation into campaigns, reporting, sales-agents, bundles, and products
• Tests — 14 new validation tests, all 239 tests pass

Design Decisions

• Validate at the resource layer, not the adapter — each method knows its schemas
• Keep hand-written types as the public API surface; schemas are runtime guards only
• Schema registry bridges auto-generated schemas to SDK methods without modifying generated code
• Response validation applied broadly; input validation only where SDK types align with OpenAPI schemas (some have diverged, e.g., advertiser brandDomain vs API brand)