OpenCode: publish the plugin as a directory so OpenCode 2 loads it

OpenCode 2 skips a plugin path that is a file ("configured plugin path must
be a directory"), so since per-run injection hcom agents in OpenCode 2 got
no plugin: only the first PTY-injected message arrived. Publish index.ts in
the runtime dir and pass the dir; OpenCode 1 and Kilo resolve a directory
without package.json to its index file, so one form serves all three.