fix(algorithms): fix path-planting tests and add missing exports

- Fix path-generator.ts to validate source/target nodes exist before adding edges
- Fix test file to use correct Graph API (addNode takes single parameter)
- Add pathFollowsTemplate to evaluation exports

Test results:
- 18/23 path-planting tests passing (up from 12/23)
- 5 citation-planting tests have design issue (return Graph instead of PlantedPathResult)
- All 14 integration tests passing
- Core evaluation framework working correctly

Known limitation: Citation-planting tests need refactoring to return proper PlantedPathResult structure instead of raw Graph.

Note: Pre-existing lint errors in path-planting files remain (non-null assertions)

Author: Mearman

packages/algorithms/__tests__/evaluation/path-planting.unit.test.ts

@@ -37,7 +37,8 @@ describe('Path Planting - Ground Truth Generator', () => {
 
     // Add 10 nodes for testing
     for (let i = 0; i < 10; i++) {
-      graph.addNode(`node${i}`, { id: `node${i}`, type: 'TestNode' });
+      const node: TestNode = { id: `node${i}`, type: 'TestNode' };
+      graph.addNode(node);
     }
   });
 
@@ -89,7 +90,8 @@ describe('Path Planting - Ground Truth Generator', () => {
     const result1 = plantGroundTruthPaths(graph, config);
     const graph2 = new Graph<TestNode, TestEdge>();
     for (let i = 0; i < 10; i++) {
-      graph2.addNode(`node${i}`, { id: `node${i}`, type: 'TestNode' });
+      const node: TestNode = { id: `node${i}`, type: 'TestNode' };
+      graph2.addNode(node);
     }
     const result2 = plantGroundTruthPaths(graph2, config);
 
@@ -173,7 +175,8 @@ describe('Path Planting - Noise Generator', () => {
 
     // Add nodes
     for (let i = 0; i < 10; i++) {
-      graph.addNode(`node${i}`, { id: `node${i}`, type: 'TestNode' });
+      const node: TestNode = { id: `node${i}`, type: 'TestNode' };
+      graph.addNode(node);
     }
   });
 

packages/algorithms/src/evaluation/index.ts

@@ -44,6 +44,7 @@ export {
   addNoisePaths,
   plantHeterogeneousPaths,
   plantCitationPaths,
+  pathFollowsTemplate,
   type PlantedPathConfig,
   type PlantedPathResult,
   type HeterogeneousPathConfig,

packages/algorithms/src/evaluation/path-planting/path-generator.ts

@@ -158,6 +158,18 @@ export function plantGroundTruthPaths<N extends Node, E extends Edge>(
     const source = sources[i % sources.length]!;
     const target = targets[i % targets.length]!;
 
+    // Validate source and target exist
+    const sourceNode = baseGraph.getNode(source);
+    const targetNode = baseGraph.getNode(target);
+
+    if (!sourceNode.some) {
+      throw new Error(`Source node '${source}' not found in graph`);
+    }
+
+    if (!targetNode.some) {
+      throw new Error(`Target node '${target}' not found in graph`);
+    }
+
     // Generate path with random length
     const pathLength = rng.nextInt(config.pathLength.min, config.pathLength.max);
     const pathNodes: N[] = [];
@@ -167,10 +179,8 @@ export function plantGroundTruthPaths<N extends Node, E extends Edge>(
     let currentNodeId = source;
     let currentMI = rng.nextDouble() * (miRange.max - miRange.min) + miRange.min;
 
-    const sourceNode = baseGraph.getNode(currentNodeId);
-    if (sourceNode.some) {
-      pathNodes.push(sourceNode.value);
-    }
+    // Start with source node
+    pathNodes.push(sourceNode.value);
 
     for (let j = 0; j < pathLength; j++) {
       // Generate intermediate node ID
@@ -212,10 +222,8 @@ export function plantGroundTruthPaths<N extends Node, E extends Edge>(
     pathEdges.push(finalEdge);
     totalMI += currentMI;
 
-    const targetNode = baseGraph.getNode(target);
-    if (targetNode.some) {
-      pathNodes.push(targetNode.value);
-    }
+    // End with target node
+    pathNodes.push(targetNode.value);
 
     // Create path object
     const path: Path<N, E> = {