Add resourceKeyResolver for rate-limit keys

[AllyMurray]

Summary

• add a non-breaking top-level resourceKeyResolver?: (url: string) => string to HttpClientOptions
• route rate-limit key resolution through a single helper used by store accounting and server cooldown handling
• preserve precedence and compatibility: resourceKeyResolver, then deprecated rateLimit.resourceExtractor, then the existing default fallback
• add coverage for default behavior, resolver precedence, legacy fallback, canProceed, getWaitTime, record, and retrieve/list normalization into one bucket
• deprecate rateLimit.resourceExtractor in the public TypeScript API and update docs to recommend resourceKeyResolver for new usage
• stabilize the SQLite adaptive rate-limit test so the full repo hook suite passes without --no-verify

Verification

• pnpm --filter @http-client-toolkit/core test
• pnpm --filter @http-client-toolkit/core build
• pnpm --filter @http-client-toolkit/store-sqlite test
• pnpm --filter @http-client-toolkit/store-sqlite build
• pnpm build
• pnpm lint
• pnpm test

All commands passed locally, and the branch was pushed with the normal pre-push hook enabled.