Investigate WCPOS-owned Expo printer module/library

[kilbot]

Context

The Expo SDK 56 / React Native 0.85 iOS build exposed a maintenance risk in react-native-esc-pos-printer@4.5.0: the package ships pre-generated New Architecture codegen output that is stale for RN 0.85 (Constants::Builder missing ResultT). We patched it locally, but this is a signal that our native printer dependency stack needs a longer-term review.

Upstream issue: tr3v3r/react-native-esc-pos-printer#249

Current WCPOS printer stack

• Epson native iOS/Android: react-native-esc-pos-printer, an unofficial RN wrapper around Epson ePOS SDK.
• Star native iOS/Android: react-native-star-io10.
• Generic native network: raw TCP on port 9100 via react-native-tcp-socket.
• Web USB/Bluetooth: @point-of-sale/webusb-receipt-printer and @point-of-sale/webbluetooth-receipt-printer.
• Web network: vendor-specific HTTP protocols (Epson ePOS, Star WebPRNT); generic raw TCP is not available in browsers.
• Generic native USB/Bluetooth: currently unsupported.

packages/printer already gives us a useful abstraction boundary (PrinterService, vendor adapters, discovery adapters), so this can probably be explored without changing printing UI flows.

Proposal to investigate

Research/design a WCPOS-owned modern printer native layer for Expo/New Architecture, potentially as one consistent package/API for:

• Epson
• Star
• Generic ESC/POS

Possible package shape:

@wcpos/expo-printer-native
  discover(options)
  printRaw(options)
  pairBluetoothDevice?(options)
  getStatus?(options)

or vendor-focused modules behind a shared JS facade:

@wcpos/expo-epson-printer
@wcpos/expo-star-printer
@wcpos/expo-generic-printer
@wcpos/printer       # existing cross-platform abstraction/facade

Questions to answer

• Should we build one native Expo module for all vendors, or separate vendor modules behind the existing @wcpos/printer abstraction?
• Can we wrap only the small native surface we need instead of exposing entire vendor SDKs?
  • Epson: discovery, raw ESC/POS via Epos2Printer.addCommand, send, status, Bluetooth pairing.
  • Star: discovery and raw print via StarIO10.
  • Generic: network TCP, and possibly native USB/Bluetooth raw writes.
• How should we package vendor binaries/licensing?
  • Epson SDK redistribution may need review before publishing publicly.
  • Internal app-only use may have fewer constraints than a public npm package.
• What is the right migration path from react-native-esc-pos-printer without breaking current printer profiles?
• What test hardware/simulator coverage do we need for Epson, Star, generic network, USB, and Bluetooth?

Success criteria for a spike

1. A minimal Expo Modules API module builds on Expo SDK 56 / RN 0.85 iOS and Android.
2. It can print raw ESC/POS bytes to at least one Epson printer using Epson's official SDK.
3. It can preserve the existing @wcpos/printer public API for app code.
4. It documents whether a single consolidated package or vendor-specific packages are the better long-term shape.