fix: guard createASTCache against zero maxSize to prevent LRU cache crash

When a repo has no parseable files (e.g., unsupported languages or all
files filtered out), chunks.reduce returns 0, causing createASTCache(0)
to pass max:0 to LRUCache which throws TypeError. This clamps maxSize
to at least 1 and adds a progress message when no parseable files exist.

gitnexus/src/core/ingestion/ast-cache.ts

@@ -10,10 +10,11 @@ export interface ASTCache {
 }
 
 export const createASTCache = (maxSize: number = 50): ASTCache => {
+  const effectiveMax = Math.max(maxSize, 1);
   // Initialize the cache with a 'dispose' handler
   // This is the magic: When an item is evicted (dropped), this runs automatically.
   const cache = new LRUCache<string, Parser.Tree>({
-    max: maxSize,
+    max: effectiveMax,
     dispose: (tree) => {
       try {
         // NOTE: web-tree-sitter has tree.delete(); native tree-sitter trees are GC-managed.
@@ -41,7 +42,7 @@ export const createASTCache = (maxSize: number = 50): ASTCache => {
 
     stats: () => ({
       size: cache.size,
-      maxSize: maxSize
+      maxSize: effectiveMax
     })
   };
 };

gitnexus/src/core/ingestion/pipeline.ts

@@ -108,6 +108,15 @@ export const runPipelineFromRepo = async (
 
     const totalParseable = parseableScanned.length;
 
+    if (totalParseable === 0) {
+      onProgress({
+        phase: 'parsing',
+        percent: 82,
+        message: 'No parseable files found — skipping parsing phase',
+        stats: { filesProcessed: 0, totalFiles: 0, nodesCreated: graph.nodeCount },
+      });
+    }
+
     // Build byte-budget chunks
     const chunks: string[][] = [];
     let currentChunk: string[] = [];

gitnexus/test/unit/ast-cache.test.ts

@@ -82,5 +82,14 @@ describe('ASTCache', () => {
       const defaultCache = createASTCache();
       expect(defaultCache.stats().maxSize).toBe(50);
     });
+
+    it('clamps maxSize of 0 to 1 to prevent LRU cache error', () => {
+      const zeroCache = createASTCache(0);
+      expect(zeroCache.stats().maxSize).toBe(1);
+      // Should still function correctly
+      const tree = mockTree('test');
+      zeroCache.set('a.ts', tree);
+      expect(zeroCache.get('a.ts')).toBe(tree);
+    });
   });
 });