Desktop sidecar crashes with bun: ESM protocol error with big-pickle

Description
OpenCode Desktop v1.18.8 on Windows 11 fails to answer any questions using the built-in opencode/big-pickle provider. The sidecar crashes with a bun: ESM protocol error.
Error from logs (%USERPROFILE%.local\share\opencode\log\opencode.log)
ERROR message="prompt_async failed" sessionID=ses_0568b3bb1ffeSNyVXN4RFCwfNz
cause="Cause([Die(Error [ERR_UNSUPPORTED_ESM_URL_SCHEME]: Only URLs with a scheme in:
file, data, node, and electron are supported by the default ESM loader.
Received protocol 'bun:')])"
Steps to reproduce

1. Install OpenCode Desktop v1.18.8 on Windows
2. Open the app, create a new session with the default opencode/big-pickle model
3. Ask any question
4. Loading hangs indefinitely; the sidecar logs show the bun: ESM error
   Expected behavior
   The desktop app should answer questions using the built-in big-pickle model, just like the CLI does.
   Actual behavior
   Every prompt_async call fails with the bun: protocol ESM error. The CLI (opencode from terminal, which runs on Bun) works fine.
   Environment

• OpenCode Desktop v1.18.8
• Windows 11
• Clean config (no plugins, no custom providers)
• Cache cleared
  Related
• PR #30324 attempted to fix Bun plugin runtime compatibility but this bun: protocol import error persists
• Issue #25880, #25824, #28287