test(analyzer): enable tree integration tests

Remove .skip after optimizing isTree/isForest predicates that caused
hanging during test execution.

Author: Mearman

src/__tests__/integration/tree.integration.test.ts

@@ -12,11 +12,7 @@ import { generateGraph } from "../../generation/generator";
 import { makeGraphSpec } from "../../generation/spec";
 import { toAnalyzerGraph } from "./helpers";
 
-// KNOWN ISSUE: This test file hangs during vitest execution (even in isolation).
-// The issue appears to be in module resolution/loading, not test execution.
-// Other integration tests in this directory work fine. Investigation pending.
-// Run with: pnpm vitest run --no-coverage src/__tests__/integration/tree.integration.test.ts
-describe.skip("Tree Graph Class", { timeout: 30_000 }, () => {
+describe("Tree Graph Class", { timeout: 30_000 }, () => {
 	describe("generation and classification roundtrip", () => {
 		it("should generate and classify a tree correctly", () => {
 			const spec = makeGraphSpec({