Plugin installer silently fails for git-based specs (github:, git+https://)

Description

Git-based plugin specs in tui.json fail silently on TUI startup. The cache directory is created but stays empty (no package.json / package-lock.json / node_modules), the plugin never loads, and nothing is logged — even with OPENCODE_LOG_LEVEL=0. No error in the TUI either.

Registry specs (pkg@latest) and file:// path specs work fine in the same environment, so it's specific to git specs. The same git spec installs fine with stock tooling: npm install "github:owner/repo#<sha>" succeeds, and node + @npmcli/arborist reify({ add: [spec] }) succeeds.

The github: shorthand resolves to ssh://git@github.com/... (no SSH keys configured here), but an explicit git+https:// spec fails the same way, so it's not just the ssh transport.

Possibly related: #8763, #21099, #47200.

Plugins

github:skolkin-worker/opencode-sessions-sidebar#2dce6f3e5ab0b344ab288df19221db5e99665be1
(also tried git+https://github.com/skolkin-worker/opencode-sessions-sidebar.git#<same sha>)
Repro plugin package: https://github.com/skolkin-worker/opencode-sessions-sidebar (has exports["./tui"], dist/ committed)

OpenCode version

1.18.30

Steps to reproduce

1. Add to ~/.config/opencode/tui.json:
   { "plugin": ["github:skolkin-worker/opencode-sessions-sidebar#2dce6f3..."] }
2. Restart the TUI
3. ~/.cache/opencode/packages/<spec>/ is created but empty; plugin not loaded; no install/load/failure entries in ~/.local/share/opencode/log/opencode.log even with OPENCODE_LOG_LEVEL=0

Same outcome with the git+https:// variant.

Screenshot and/or share link

— (no error UI to screenshot; the only artifact is the empty cache dir)

Operating System

macOS 26.5.2 (arm64)

Terminal

WezTerm