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/package.json

@@ -2,12 +2,12 @@
   "name": "@fusion-plugin-examples/roadmap",
   "version": "0.1.0",
   "type": "module",
-  "description": "Roadmap domain and plugin manifest package for Fusion",
+  "description": "Roadmap backend plugin for Fusion",
   "private": true,
   "exports": {
     ".": {
       "types": "./src/index.ts",
-      "import": "./dist/index.js"
+      "import": "./src/index.ts"
     }
   },
   "scripts": {
@@ -16,7 +16,8 @@
   },
   "dependencies": {
     "@fusion/core": "workspace:*",
-    "@fusion/plugin-sdk": "workspace:*"
+    "@fusion/plugin-sdk": "workspace:*",
+    "express": "^5.1.0"
   },
   "devDependencies": {
     "@types/node": "^25.5.2",