test: enforce test-directory isolation across all packages

Introduce a shared test-utils module and global vitest setup that
guarantee tests never write to the real .fusion directory or leak temp
directories under /tmp.

Infrastructure:
- packages/core/src/__test-utils__/workspace.ts — tempWorkspace(),
  useIsolatedCwd(), trackForCleanup(), assertOutsideRealFusion() with
  auto-cleanup in afterEach.
- packages/core/src/__test-utils__/vitest-setup.ts — per-worker guard:
  chdirs each worker into an isolated tmp dir, wraps process.chdir to
  refuse the real .fusion, scopes tmp dirs under fusion-test-workers/
  (skips cwd change in thread-pool workers where chdir isn't supported).
- packages/core/src/__test-utils__/vitest-teardown.ts — globalSetup
  hook that wipes the shared parent even when workers are SIGKILLed.
- scripts/check-test-isolation.mjs + `test:isolated` / `test:check-
  isolation` scripts for CI.
- @fusion/test-utils alias + setupFiles + globalSetup wired into core,
  cli, engine, dashboard, tui vitest configs; matching tsconfig paths.

Test refactors (no behavior change):
- cli provider-settings, auth-paths, provider-auth — switch leaking
  mkdtempSync calls to tempWorkspace().
- core migration, first-run, store-backward-compat — replace manual
  process.chdir save/restore with useIsolatedCwd().
- tui fusion-context — replace 9 hardcoded tmp paths (collision-prone
  under parallelism) with tempWorkspace().
- dashboard useTheme, FileBrowser, TaskCard — resolve source-file reads
  against a PACKAGE_ROOT computed from import.meta.url instead of cwd,
  so tests don't depend on the process working directory.

Verified: full suite (~15,500 tests across 8 packages + plugins) passes
and the orphan-detector reports zero leaked temp directories after a
complete run.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/dashboard/app/components/__tests__/FileBrowser.test.tsx

@@ -1,10 +1,15 @@
 import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
 import { render, screen, fireEvent, waitFor, cleanup, act } from "@testing-library/react";
 import { readFileSync } from "node:fs";
-import { resolve } from "node:path";
+import { dirname, resolve } from "node:path";
+import { fileURLToPath } from "node:url";
 import { FileBrowser } from "../FileBrowser";
 import type { FileNode } from "../../api";
 
+// Resolve paths relative to this test file so tests pass regardless of cwd
+// (a global test safety guard may change cwd to a per-worker temp dir).
+const PACKAGE_ROOT = resolve(dirname(fileURLToPath(import.meta.url)), "../../..");
+
 // ── Mocks ───────────────────────────────────────────────────────────────
 
 vi.mock("lucide-react", async () => {
@@ -370,7 +375,7 @@ describe("FileBrowser", () => {
   });
 
   it("defines mobile-friendly touch targets for context menu items", () => {
-    const cssPath = resolve(process.cwd(), "app/styles.css");
+    const cssPath = resolve(PACKAGE_ROOT, "app/styles.css");
     const css = readFileSync(cssPath, "utf8");
     expect(css).toMatch(/\.file-browser-context-menu__item\s*\{[^}]*min-height:\s*36px;/);
   });

packages/dashboard/app/components/__tests__/TaskCard.test.tsx

@@ -5,6 +5,12 @@ import type { Column, Task, TaskDetail } from "@fusion/core";
 import { TaskCard } from "../TaskCard";
 import React, { useState } from "react";
 import { readFileSync } from "node:fs";
+import { dirname, resolve } from "node:path";
+import { fileURLToPath } from "node:url";
+
+// Resolve paths relative to this test file so tests pass regardless of cwd
+// (a global test safety guard may change cwd to a per-worker temp dir).
+const PACKAGE_ROOT = resolve(dirname(fileURLToPath(import.meta.url)), "../../..");
 
 vi.mock("../../api", () => ({
   fetchTaskDetail: vi.fn(),
@@ -3599,7 +3605,7 @@ describe("TaskCard agent badge", () => {
       expect(text).toBeInTheDocument();
     });
 
-    const styles = readFileSync("app/styles.css", "utf-8");
+    const styles = readFileSync(resolve(PACKAGE_ROOT, "app/styles.css"), "utf-8");
     expect(styles).toMatch(/\.card-agent-badge\s*\{[^}]*flex-shrink:\s*0;/);
     expect(styles).toMatch(/\.card-agent-badge\s*\{[^}]*max-width:\s*120px;/);
     expect(styles).toMatch(/\.card-agent-badge-text\s*\{[^}]*text-overflow:\s*ellipsis;/);

packages/dashboard/app/hooks/__tests__/useTheme.test.ts

@@ -1,10 +1,16 @@
 import { readFileSync } from "node:fs";
+import { dirname, resolve } from "node:path";
+import { fileURLToPath } from "node:url";
 import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
 import { renderHook, act, waitFor } from "@testing-library/react";
 import { COLOR_THEMES, type Settings } from "@fusion/core";
 import { useTheme, getThemeInitScript } from "../useTheme";
 import { fetchGlobalSettings, updateGlobalSettings } from "../../api";
 
+// Resolve paths relative to this test file so tests pass regardless of cwd
+// (a global test safety guard may change cwd to a per-worker temp dir).
+const PACKAGE_ROOT = resolve(dirname(fileURLToPath(import.meta.url)), "../../..");
+
 vi.mock("../../api", () => ({
   fetchGlobalSettings: vi.fn(),
   updateGlobalSettings: vi.fn(),
@@ -433,8 +439,8 @@ describe("useTheme", () => {
   it("applies factory-specific design tokens from the stylesheet", () => {
     // Load both base styles and theme data (theme blocks are in a separate file)
     const style = document.createElement("style");
-    const baseCss = readFileSync("app/styles.css", "utf8");
-    const themeDataCss = readFileSync("app/public/theme-data.css", "utf8");
+    const baseCss = readFileSync(resolve(PACKAGE_ROOT, "app/styles.css"), "utf8");
+    const themeDataCss = readFileSync(resolve(PACKAGE_ROOT, "app/public/theme-data.css"), "utf8");
     style.textContent = baseCss + "\n" + themeDataCss;
     document.head.appendChild(style);
 
@@ -1145,7 +1151,7 @@ describe("getThemeInitScript", () => {
   });
 
   it("keeps index.html inline theme validation in sync with supported themes", () => {
-    const indexHtml = readFileSync("app/index.html", "utf8");
+    const indexHtml = readFileSync(resolve(PACKAGE_ROOT, "app/index.html"), "utf8");
 
     COLOR_THEMES.forEach((theme) => {
       expect(indexHtml).toContain(`'${theme}'`);
@@ -1164,7 +1170,7 @@ describe("getThemeInitScript", () => {
   it("index.html uses correct URL replacement pattern", () => {
     // Verify that the inline script in index.html uses the correct URL replacement
     // pattern (handle both directory paths and filename paths) rather than buggy concatenation
-    const indexHtml = readFileSync("app/index.html", "utf8");
+    const indexHtml = readFileSync(resolve(PACKAGE_ROOT, "app/index.html"), "utf8");
 
     // The correct pattern: check if base ends with '/' and use slice or replace accordingly
     // The buggy pattern: base.substring(0, 7) + dirPath + 'theme-data.css'

packages/dashboard/tsconfig.json

@@ -4,7 +4,10 @@
     "outDir": "dist",
     "rootDir": "src",
     "jsx": "react-jsx",
-    "types": ["node", "vitest/globals", "@testing-library/jest-dom"]
+    "types": ["node", "vitest/globals", "@testing-library/jest-dom"],
+    "paths": {
+      "@fusion/test-utils": ["../core/src/__test-utils__/workspace.ts"]
+    }
   },
   "include": ["src/**/*"],
   "exclude": ["src/**/*.test.ts", "src/**/*.test.tsx", "src/**/__tests__/**/*"]

packages/dashboard/vitest.config.ts

@@ -13,13 +13,18 @@ export default defineConfig({
     alias: {
       "@fusion/core": resolve(__dirname, "../core/src/index.ts"),
       "@fusion/engine": resolve(__dirname, "../engine/src/index.ts"),
+      "@fusion/test-utils": resolve(__dirname, "../core/src/__test-utils__/workspace.ts"),
     },
   },
   test: {
     environment: "jsdom",
     globals: true,
     include: ["app/**/*.test.{ts,tsx}", "src/**/*.test.{ts,tsx}"],
-    setupFiles: ["./vitest.setup.ts"],
+    setupFiles: [
+      resolve(__dirname, "../core/src/__test-utils__/vitest-setup.ts"),
+      "./vitest.setup.ts",
+    ],
+    globalSetup: [resolve(__dirname, "../core/src/__test-utils__/vitest-teardown.ts")],
     maxWorkers,
     poolOptions: { threads: { minThreads: 1, maxThreads: maxWorkers }, forks: { minForks: 1, maxForks: maxWorkers } },
     fileParallelism: true,