feat!: add defineOptions factory for fetchify options - #2

Summary

• Add defineOptions(options: FetchifyOptions): FetchifyOptions, a typed entry point for authoring fetchify options independently of createFetchify (mirrors the defineConfig pattern from Vite/Vue).
• BREAKING: rename CreateFetchifyOptions to FetchifyOptions, the shared type now used by both defineOptions and createFetchify.
• Export defineOptions and FetchifyOptions from both the fetchify and fetchify/native entry points.

const options = defineOptions({ baseUrl: new URL("https://api.packetify.app") });
const http = createFetchify(options);
const response = http.GET("/users");

Implements the define-fetchify-options OpenSpec change (archived at openspec/changes/archive/2026-08-02-define-fetchify-options/); main specs fetchify-options and http-client updated accordingly. Changeset included (minor, package is unreleased/private at 0.0.0).

Test plan

• bun test — 27 pass, 0 fail
• bun run build — builds cleanly, dist/lib/define-options.d.ts generated with no type errors

🤖 Generated with Claude Code