bug: opencode-plugin folder not included in install zip #149

The resources/opencode-plugin/ folder is not present in the distributed .zip release.

Steps to reproduce:

1. Download the latest wmux--win-x64.zip from the releases page
2. Extract it
3. Look in resources/ — there is no opencode-plugin/ folder

Expected: resources/opencode-plugin/wmux.js should be present in the release zip, the same way wmux-orchestrator/ is.

Why it matters: the OpenCode plugin is required for OpenCode integration, and is missing from the zip.