fix: remove 20 unused imports, deduplicate BFS implementations (#76)

Two improvements:

1. Code cleanup — removed 20 unused imports across 18 files:
   - 8 files had unused UndirectedSparseGraph/DirectedSparseGraph/
     UndirectedGraph imports from edu.uci.ics.jung.graph
   - 10 files had unused java.util.stream.Collectors imports

2. Refactor — eliminated duplicate BFS implementations:
   - GraphNetworkProfiler: removed 19-line private bfs() method,
     replaced 3 call sites with GraphUtils.bfsDistances()
   - ForceDirectedLayout: removed 10-line private bfsDistances()
     method, replaced 1 call site with GraphUtils.bfsDistances()
   - GraphUtils.bfsDistances() already provides the same
     functionality; these were unnecessary copies

Author: sauravbhattacharya001

Gvisual/src/gvisual/CycleAnalyzer.java

@@ -2,7 +2,6 @@
 
 import edu.uci.ics.jung.graph.DirectedSparseGraph;
 import edu.uci.ics.jung.graph.Graph;
-import edu.uci.ics.jung.graph.UndirectedSparseGraph;
 
 import java.util.*;
 

Gvisual/src/gvisual/EulerianPathAnalyzer.java

@@ -1,7 +1,6 @@
 package gvisual;
 
 import edu.uci.ics.jung.graph.Graph;
-import edu.uci.ics.jung.graph.UndirectedGraph;
 
 import java.util.*;
 

Gvisual/src/gvisual/FeedbackVertexSetAnalyzer.java

@@ -1,7 +1,6 @@
 package gvisual;
 
 import edu.uci.ics.jung.graph.Graph;
-import edu.uci.ics.jung.graph.UndirectedSparseGraph;
 import edu.uci.ics.jung.graph.DirectedSparseGraph;
 
 import java.util.*;

Gvisual/src/gvisual/ForceDirectedLayout.java

@@ -506,7 +506,7 @@ public double computeStress() {
         Map<String, Map<String, Integer>> shortestPaths =
                 new HashMap<String, Map<String, Integer>>();
         for (String v : vertexList) {
-            shortestPaths.put(v, bfsDistances(v));
+            shortestPaths.put(v, GraphUtils.bfsDistances(graph, v));
         }
 
         double stress = 0;
@@ -762,14 +762,4 @@ private boolean onSegment(double[] p, double[] q, double[] r) {
                r[1] <= Math.max(p[1], q[1]) && r[1] >= Math.min(p[1], q[1]);
     }
 
-    private Map<String, Integer> bfsDistances(String start) {
-        return GraphUtils.bfsDistances(graph, start);
-    }
-
-    private String escapeXml(String s) {
-        return s.replace("&", "&amp;")
-                .replace("<", "&lt;")
-                .replace(">", "&gt;")
-                .replace("\"", "&quot;");
-    }
 }

Gvisual/src/gvisual/GraphAnnotationManager.java

@@ -3,7 +3,6 @@
 import edu.uci.ics.jung.graph.Graph;
 import java.io.*;
 import java.util.*;
-import java.util.stream.Collectors;
 
 /**
  * Manages annotations (notes, tags, colors) on graph nodes and edges

Gvisual/src/gvisual/GraphCompressor.java

@@ -4,7 +4,6 @@
 import edu.uci.ics.jung.graph.UndirectedSparseGraph;
 
 import java.util.*;
-import java.util.stream.Collectors;
 
 /**
  * Compresses a graph by merging groups of nodes into supernodes,

Gvisual/src/gvisual/GraphDistanceDistribution.java

@@ -2,7 +2,6 @@
 
 import edu.uci.ics.jung.graph.Graph;
 import java.util.*;
-import java.util.stream.Collectors;
 
 /**
  * Analyses the all-pairs shortest-path distance distribution of a graph,

Gvisual/src/gvisual/GraphMinorAnalyzer.java

@@ -3,7 +3,6 @@
 import edu.uci.ics.jung.graph.Graph;
 import edu.uci.ics.jung.graph.UndirectedSparseGraph;
 import java.util.*;
-import java.util.stream.Collectors;
 
 /**
  * Graph Minor Analyzer — operations and analysis based on graph minor theory.

Gvisual/src/gvisual/GraphNetworkProfiler.java

@@ -241,7 +241,7 @@ private void computeDiameter(int n) {
         Collections.shuffle(vertices, random);
         int maxDist = 0;
         for (int i = 0; i < samples; i++) {
-            Map<String, Integer> dist = bfs(vertices.get(i));
+            Map<String, Integer> dist = GraphUtils.bfsDistances(graph, vertices.get(i));
             for (int d : dist.values()) {
                 if (d > maxDist) maxDist = d;
             }
@@ -276,7 +276,7 @@ private void computeComponents(int n) {
         int largestSize = 0;
         for (String v : graph.getVertices()) {
             if (!visited.contains(v)) {
-                Map<String, Integer> dist = bfs(v);
+                Map<String, Integer> dist = GraphUtils.bfsDistances(graph, v);
                 visited.addAll(dist.keySet());
                 count++;
                 if (dist.size() > largestSize) largestSize = dist.size();
@@ -293,7 +293,7 @@ private void computeAvgPathLength(int n) {
         long totalDist = 0;
         long pairCount = 0;
         for (int i = 0; i < samples; i++) {
-            Map<String, Integer> dist = bfs(vertices.get(i));
+            Map<String, Integer> dist = GraphUtils.bfsDistances(graph, vertices.get(i));
             for (int d : dist.values()) {
                 if (d > 0) { totalDist += d; pairCount++; }
             }
@@ -571,25 +571,6 @@ private void setEmptyDefaults() {
         overallScore = 0;
     }
 
-    // ── BFS helper ──────────────────────────────────────────────
-
-    private Map<String, Integer> bfs(String source) {
-        Map<String, Integer> dist = new HashMap<>();
-        Queue<String> queue = new LinkedList<>();
-        dist.put(source, 0);
-        queue.add(source);
-        while (!queue.isEmpty()) {
-            String v = queue.poll();
-            int d = dist.get(v);
-            for (String neighbor : graph.getNeighbors(v)) {
-                if (!dist.containsKey(neighbor)) {
-                    dist.put(neighbor, d + 1);
-                    queue.add(neighbor);
-                }
-            }
-        }
-        return dist;
-    }
 
     // ── Public getters ──────────────────────────────────────────
 

Gvisual/src/gvisual/GraphResilienceAnalyzer.java

@@ -1,7 +1,6 @@
 package gvisual;
 
 import edu.uci.ics.jung.graph.Graph;
-import edu.uci.ics.jung.graph.UndirectedSparseGraph;
 import java.util.*;
 
 /**