plugins: npm/git subprocesses pop console windows on Windows during plugin install/reload #52299

Summary

When OpenCode loads or reloads plugins referenced as github:... packages, the
spawned npm install / git subprocesses each open a visible console window on
Windows. When a plugin fails to install, the server retries on a loop (~every 15s),
popping a new console window on every retry.

Environment

• opencode version: 2.0.20
• OS: Windows 11 (Windows_NT 10.0.26200, win32 x64)
• Terminal: VS Code terminal (TERM_PROGRAM=vscode)
• Shell: Git Bash (C:\Program Files\Git\usr\bin\bash.exe)
• Install/channel: latest
• Active plugins: @tarquinen/opencode-dcp, @wakatime/opencode-wakatime, github:rafaelsnv/opencode-handoff, github:rafaelsnv/opencode-md-table-formatter

Reproduction

1. On Windows, configure a plugin as a github: reference, e.g. "plugins": ["github:owner/some-plugin"].
2. Start opencode or reload the service (opencode service restart).
3. Observe console windows flashing/popping while the plugin is installed into ~/.cache/opencode/npm/....
4. If the plugin install fails (e.g. git dep preparation failed), a new console window pops roughly every 15 seconds as the server retries the install indefinitely.

Expected Behavior

Plugin installation subprocesses (npm, git) should not open visible console
windows on Windows — child processes should be spawned with windowsHide: true
(or equivalent), and a permanently failing plugin install should back off instead
of retrying in a tight loop.

Actual Behavior

Every install/retry spawns a subprocess that opens a console window. Observed in
the log (repeated every ~15s while a failing plugin was configured):

timestamp=... level=INFO message="cli starting" version=2.0.20 args="[\"B:\\~BUN\\bin\\npm-cli.js\",\"install\",\"--force\",\"--cache=C:\\Users\\...\\npm-cache\",...]" role=cli
timestamp=... level=ERROR message="cli process failed" cause="Cause([Fail(~effect/cli/CliError/ShowHelp: Help requested)])" role=cli
timestamp=... level=WARN message="failed to load plugin" target=github:.../opencode-supabase cause="Cause([Fail(NpmInstallFailedError (cause: Error: git dep preparation failed))])" role=server

Additional Context

• Secondary issue visible in the same logs: the npm invocation runs through a Bun
  shim (B:\~BUN\bin\npm-cli.js) and fails immediately with ShowHelp: Help requested,
  so plugin installs appear to never actually succeed through that path (working
  loads came from an already-populated cache).
• Workaround: reference plugins by local directory path instead of github: refs —
  local plugin loading performs no subprocess spawn and does not pop windows.