Fill no-one's-land gaps between merged sub-regions (v0.17.0)

Part of #16

package.json

@@ -1,6 +1,6 @@
 {
   "name": "history",
-  "version": "0.16.0",
+  "version": "0.17.0",
   "private": true,
   "type": "module",
   "description": "AI-driven alternate-history simulator — the LLM is the world engine (Pax Historia style).",
@@ -13,6 +13,7 @@
     "coarsen:regions": "node scripts/coarsen-regions.mjs",
     "cleanup:regions": "node scripts/cleanup-regions.mjs",
     "smooth:regions": "node scripts/smooth-regions.mjs",
+    "fill:regions": "node scripts/fill-gaps.mjs",
     "typecheck": "tsc --noEmit",
     "lint": "eslint .",
     "e2e": "playwright test"
@@ -42,7 +43,14 @@
     "@eslint/js": "^9.20.0",
     "@playwright/test": "^1.62.1",
     "@tailwindcss/vite": "^4.1.4",
+    "@turf/area": "^7.4.0",
+    "@turf/bbox": "^7.4.0",
+    "@turf/boolean-point-in-polygon": "^7.4.0",
+    "@turf/centroid": "^7.4.0",
+    "@turf/difference": "^7.4.0",
+    "@turf/distance": "^7.4.0",
     "@turf/simplify": "^7.4.0",
+    "@turf/turf": "^7.4.0",
     "@turf/union": "^7.4.0",
     "@types/better-sqlite3": "^7.6.13",
     "@types/express": "^4.17.25",