fix: add depth=-1 test case and remove premature symbols mention in depth description

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: tae2089

internal/mcp/server.go

@@ -266,7 +266,7 @@ func NewServer(deps *Deps) *server.MCPServer {
 			Tool: mcp.NewTool("get_rag_tree",
 				mcp.WithDescription("Get the RAG document tree for navigation. Call without arguments first to see all communities, then pass community_id to drill into a specific one."),
 				mcp.WithString("community_id", mcp.Description("Community node ID as shown in the tree (e.g. 'community:auth'). Omit to get the full tree.")),
-				mcp.WithNumber("depth", mcp.Description("Maximum tree depth to return (1=communities only, 2=communities+files, 3=including symbols). Default: 0 (unlimited).")),
+				mcp.WithNumber("depth", mcp.Description("Maximum tree depth to return (1=communities only, 2=communities+files). Default: 0 (unlimited).")),
 			),
 			Handler: h.getRagTree,
 		},

internal/ragindex/builder_test.go

@@ -366,12 +366,14 @@ func TestPruneTree_NegativeDepth(t *testing.T) {
 		},
 	}
 
-	result := ragindex.PruneTree(root, 0)
-	if len(result.Children) != 1 {
-		t.Fatalf("expected 1 child, got %d", len(result.Children))
-	}
-	if len(result.Children[0].Children) != 1 {
-		t.Fatalf("expected 1 grandchild at depth=0 (unlimited), got %d", len(result.Children[0].Children))
+	for _, depth := range []int{0, -1} {
+		result := ragindex.PruneTree(root, depth)
+		if len(result.Children) != 1 {
+			t.Fatalf("depth=%d: expected 1 child, got %d", depth, len(result.Children))
+		}
+		if len(result.Children[0].Children) != 1 {
+			t.Fatalf("depth=%d: expected 1 grandchild (unlimited), got %d", depth, len(result.Children[0].Children))
+		}
 	}
 }