plugins for V2: local plugin paths fail to load (file entries rejected, @opencode/plugin unresolvable)

Description

A local plugin cannot be loaded by following the documentation.

1. A plugins entry pointing at a .ts file is rejected with
   WARN "configured plugin path must be a directory", and the plugin never loads. The plugins
   documentation shows exactly this form (./plugins/local, ../shared/plugin.ts,
   /absolute/path/plugin.ts, file:///home/me/plugins/local).

2. An entry pointing at a directory (or a plugin discovered under .opencode/plugins/) is found and
   imported, but loading fails because the documented import is not resolvable:

   level=INFO  message="loading plugin"  id=…/mi-plugin  entrypoint=file:///…/mi-plugin/index.ts
   level=WARN  message="failed to load plugin"
     cause="Cause([Die(ResolveMessage: Cannot find package '@opencode/plugin' imported from …\mi-plugin\index.ts)])"
   

   This happens with both loading paths (config entry and discovery). It only works if the plugin
   directory ships its own node_modules.

In both cases the failure is silent outside the log — no error in the session, no hint in the TUI —
so the only visible symptom is that the plugin's tools and hooks do not exist.

Plugins

None configured globally. The reproductions use a single project entry in opencode.jsonc and a
directory under .opencode/plugins/.

OpenCode version

2.0.3 (@opencode/cli installed globally with npm)

Steps to reproduce

A. plugins entry pointing at a .ts file

1. Create a local plugin with a single default export: export default { id: "x", setup() {} }.

2. Configure the entry: { "plugins": ["C:/absolute/path/mi-plugin/index.ts"] }.

3. Start any session in that project (opencode run --standalone --print-logs --log-level info).

   Log: level=WARN message="configured plugin path must be a directory" target=C:/absolute/path/mi-plugin/index.ts

B. Directory entry or .opencode/plugins/ discovery importing @opencode/plugin

1. Create <project>/.opencode/plugins/mi-plugin/index.ts:

   import { Plugin } from "@opencode/plugin"
   
   export default Plugin.define({
     id: "mi-plugin",
     async setup() {},
   })
   

2. Start a session in that project.

   The module is found, then loading fails with the Cannot find package '@opencode/plugin' cause above.

Screenshot and/or share link

N/A — both failures are only visible in the server log; the log lines are quoted above.

Operating System

Windows 10 Enterprise LTSC 10.0.19044 (x64)

Terminal

Not applicable: reproduced headlessly with opencode run --standalone from PowerShell 5.1
(TERM=xterm-256color, TERM_PROGRAM unset, %COMSPEC% = cmd.exe).

Additional context (not part of the form):

• Workarounds that work: export a plain object (export default { id, setup }) instead of
  Plugin.define; or run an install inside the plugin directory so @opencode/plugin resolves
  locally (@opencode/plugin@2.0.5 is published on npm).
• Why this matters: the first case is a documentation/behaviour mismatch, and the second blocks
  every local (non-published) plugin that follows the documented import. Both fail silently, which
  makes them expensive to diagnose.
• Notes: tested with the path written as C:/… and C:\…; opencode plugin list does not load
  project plugins, so it cannot be used to verify. Reproduced consistently on 2.0.3.