Refactor: Replace heuristic SCC solver with LP-based solver

package.json

@@ -33,6 +33,7 @@
     "i18next": "^25.6.3",
     "i18next-browser-languagedetector": "^8.2.0",
     "i18next-http-backend": "^3.0.2",
+    "javascript-lp-solver": "^1.0.3",
     "lucide-react": "^0.552.0",
     "radix-ui": "^1.4.3",
     "react": "^19.1.1",

src/components/mappers/merged-mapper.ts

@@ -411,6 +411,12 @@ export function mapPlanToFlowMerged(
         node.recipe.craftingTime,
       ) * node.facilityCount;
 
+    // Defensive: skip phantom sinks below display threshold. The calculator
+    // already filters via SURPLUS_EPSILON; this guards against any future
+    // path that injects a near-zero disposal recipe and prevents an isolated
+    // node from violating flow integrity.
+    if (disposalRate <= 0.001) return;
+
     disposalSinkNodes.push(
       createDisposalSinkNode(
         disposalSinkId,

src/components/mappers/separated-mapper.ts

@@ -749,6 +749,12 @@ export function mapPlanToFlowSeparated(
         node.recipe.craftingTime,
       ) * node.facilityCount;
 
+    // Defensive: skip phantom sinks below display threshold. The calculator
+    // already filters via SURPLUS_EPSILON; this guards against any future
+    // path that injects a near-zero disposal recipe and prevents an isolated
+    // node from violating flow integrity.
+    if (disposalRate <= 0.001) return;
+
     disposalSinkNodes.push(
       createDisposalSinkNode(
         disposalSinkId,

src/lib/calculator-types.ts

@@ -1,7 +1,5 @@
 import type { ItemId, RecipeId, FacilityId, Item, Recipe, Facility } from "@/types";
 
-export type SystemRow = { row: number[]; rhs: number; itemId: ItemId };
-
 export type ProductionMaps = {
   itemMap: Map<ItemId, Item>;
   recipeMap: Map<RecipeId, Recipe>;

src/lib/calculator.ts

@@ -23,6 +23,15 @@ import type {
   InvalidSCCInfo,
 } from "./calculator-types";
 
+// Tolerance for floating-point residuals in surplus mass balance.
+// LP facility counts can be fractions like 1/6 that don't have exact binary
+// representations; recombining `production - consumption - target` can leave
+// residuals on the order of 1e-13. Without this tolerance, a disposal recipe
+// would be injected with facilityCount ≈ 0, rendering as a disconnected
+// "0/min" sink in the UI (e.g. Xircon Effluent on Jade Gourd at 1/min).
+// Matches `TARGET_VALIDATION_TOLERANCE` used by the LP solver.
+const SURPLUS_EPSILON = 1e-6;
+
 function injectDisposalRecipes(
   graph: BipartiteGraph,
   flowData: FlowData,
@@ -65,7 +74,7 @@ function injectDisposalRecipes(
     const targetDemand = targets.find((t) => t.itemId === itemId)?.rate || 0;
 
     const surplus = totalProduction - totalConsumption - targetDemand;
-    if (surplus <= 0) continue;
+    if (surplus <= SURPLUS_EPSILON) continue;
 
     const disposalRecipe = Array.from(maps.recipeMap.values()).find(
       (r) =>