v1.13.0 - Cloudflare Workers AI cache binding support

Added

• Cloudflare Workers AI run options now translate CacheHints.sessionId into x-session-affinity for provider-prefix and both cache strategies, including streaming and raw vision calls.
• CloudflareConfig.gateway exposes typed Workers AI binding Gateway options and merges request cache metadata into the third env.AI.run() argument.
• Cloudflare usage parsing now normalizes Workers AI cached input token counts into TokenUsage.cachedInputTokens.

Validation

• npm run typecheck
• npm test
• npm run test:package
• npm audit --omit=dev

Closes #84.