Epic: JavaScript/WASM bindings with fusio

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Summary

Provide first-class JavaScript bindings for Tonbo via WebAssembly, supporting browser, Node.js, Deno, Bun, and Cloudflare Workers. Leverage fusio's executor abstraction to deliver native Promise integration across all runtimes, with platform-appropriate storage backends (OPFS, filesystem, R2/S3).

Current State

• WASM compilation works (wasm32-unknown-unknown target)
• Cloudflare Worker example exists
• No npm package
• No browser support (OPFS)
• No Node.js/Deno/Bun support
• No Arrow JS interop
• No TypeScript types

Why Multi-Runtime?

┌────────────────────────────────────────────────────────────┐
│                    JavaScript Runtimes                     │
├─────────────┬─────────────┬─────────────┬──────────────────┤
│   Browser   │   Node.js   │    Deno     │ Cloudflare/Edge  │
├─────────────┼─────────────┼─────────────┼──────────────────┤
│   OPFS      │     fs      │   Deno.fs   │    R2 / KV       │
│  IndexedDB  │    S3 SDK   │   S3 SDK    │  Durable Objects │
│  (fallback) │             │             │                  │
└─────────────┴─────────────┴─────────────┴──────────────────┘

Each runtime has different:

• File system APIs
• Async primitives
• Module systems (ESM, CJS)
• Bundle constraints

Goals

1. Single npm package: npm install @tonbo/core works everywhere
2. Runtime detection: Auto-select appropriate storage/executor
3. Arrow JS interop: Zero-copy where possible with apache-arrow
4. TypeScript-first: Full type definitions
5. Tree-shakeable: Minimal bundle for browser
6. Promise-native: Idiomatic async/await

Non-Goals

• React/Vue/Svelte framework bindings (future)
• GraphQL/REST API layer (user responsibility)
• Offline-first sync engine (separate project)
• Legacy browser support (modern browsers only)

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DEV-514