feat(FN-3638): extract roadmap domain into plugin and define plugin route s

This merge restructures the roadmap plugin by removing its duplicated domain logic (roadmap store, ordering, handoff, and types — ~3,000 lines deleted) and completing the plugin SDK scaffold with proper route status/body contracts and type exports. It also introduces eval settings infrastructure wit

Fusion-Task-Id: FN-3638

packages/plugin-sdk/src/index.ts

@@ -49,6 +49,8 @@ export type {
   PluginToolResult,
   PluginRouteDefinition,
   PluginRouteMethod,
+  PluginRouteResponse,
+  PluginRouteResult,
   PluginUiSurface,
   PluginUiSlotDefinition,
   PluginUiContributionSurface,