Plugin load failures are published to the event bus but never logged

Description

publishPluginError in packages/opencode/src/plugin/index.ts is the only sink for the four loadExternal failure stages (install, entry, compatibility, load): it publishes a Session.Event.Error and never touches the logger. Under ACP nothing consumes that event — Subscription.handle in packages/opencode/src/acp/event.ts has no session.error case — so a failed plugin leaves no trace anywhere. opencode exits 0 and serves the session with a reduced tool set.

It is the lone exception in its own function: applyPlugin twenty lines below, internal plugins, config hooks and dispose hooks all report through Effect.logError.

This cost us two sessions answering with all twelve of their Mattermost tools missing, against a production log with zero matches for Failed to install plugin\|Failed to load plugin\|skipped:.

Ask: log spec, stage and message alongside the event publish. Happy to send a PR.

Related: #42379 (open) adds a stderr write; #44367 is the same silence on Desktop; #46587 covers the missing() no-op.

OpenCode version

1.18.25

Steps to reproduce

1. Add any npm/git plugin spec to opencode.jsonc and clear the plugin cache.
2. Make the install fail: unshare -r -n opencode acp.
3. The plugin's tools are absent, exit code is 0, and the log says nothing. The same failure in the TUI does surface an error.