285d384ca6
discoverAgents only walked .omp/agents and Claude marketplace plugin roots, so agents shipped by OMP npm plugins (omp plugin install ...) and --extension/extensions: settings roots silently disappeared while their sibling skills/, hooks/, tools/ subdirectories were already discovered. Route the same listOmpExtensionRoots scan used by discovery/omp-plugins.ts through discoverAgents and append <root>/agents to the ordered scan list, project scope before user. listOmpExtensionRoots already filters Claude marketplace installs by realpath so they continue to flow only through the claude-plugins provider. Fixes #3920