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

plugins/fusion-plugin-roadmap/src/roadmap-suggestions.ts

@@ -0,0 +1 @@
+export {};