FN-6627: guard dist-barrel tests on complete core dist

Align dist-barrel regression guards so partial @fusion/core dist artifacts skip instead of failing mismatched dependency checks.

- Add a shared @fusion/test-utils predicate for complete built core dist barrels.
- Use the predicate in CLI and core dist-barrel regression tests before importing runtime dist modules.
- Cover absent and partial dist directories with focused predicate tests.

Files changed:
 packages/cli/src/__tests__/extension.test.ts       |  9 +++--
 .../src/__test-utils__/__tests__/core-dist.test.ts | 46 ++++++++++++++++++++++
 packages/core/src/__test-utils__/workspace.ts      | 11 ++++++
 .../core/src/__tests__/task-list-format.test.ts    | 17 ++++----
 4 files changed, 72 insertions(+), 11 deletions(-)

Fusion-Task-Id: FN-6627

Fusion-Task-Lineage: a05ad009-229d-44c2-a49d-2d9b3f3d6094

packages/cli/src/__tests__/extension.test.ts

@@ -1,5 +1,4 @@
 import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
-import { existsSync } from "node:fs";
 import { mkdtemp, mkdir, rm, writeFile } from "node:fs/promises";
 import { dirname, join, resolve } from "node:path";
 import { tmpdir } from "node:os";
@@ -27,6 +26,7 @@ import kbExtension, { resolveTaskListFormatter } from "../extension.js";
 import { TaskStore, AgentStore, MANUAL_RETRY_RESET_COUNTER_KEYS, RESEARCH_RUN_STATUSES, MAX_TASK_LIST_TEXT_CHARS, formatTaskListText } from "@fusion/core";
 import type { WorkflowIr } from "@fusion/core";
 import { isGhAvailable, isGhAuthenticated, runGhJsonAsync } from "@fusion/core/gh-cli";
+import { hasBuiltCoreDistBarrel } from "@fusion/test-utils";
 import { runTaskPlan } from "../commands/task.js";
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
@@ -2694,13 +2694,14 @@ describe("fn pi extension (runnable structured-output regression slice)", () =>
     /**
      * FNXC:TaskListOutput 2026-06-17-02:37:
      * FN-6535 reproduces the heartbeat failure at the actual CLI tool surface while forcing @fusion/core to resolve through the built dist barrel. The normal CLI suite aliases @fusion/core to source, so this targeted mock is the regression guard for stale exports.import dist artifacts.
+     *
+     * FNXC:CoreTests 2026-06-18-01:35:
+     * FN-6627 aligns the skip gate with every built @fusion/core dist artifact this runtime-dist mock loads, so a partial stale dist skips cleanly while a complete dist still exercises the heartbeat fn_task_list surface.
      */
-    it.skipIf(!existsSync(resolve(__dirname, "../../../core/dist/index.js")))(
+    it.skipIf(!hasBuiltCoreDistBarrel(resolve(__dirname, "../../../core/dist")))(
       "executes with @fusion/core resolved through the built dist barrel",
       async () => {
         const distCoreIndex = resolve(__dirname, "../../../core/dist/index.js");
-        const distTaskListFormat = resolve(__dirname, "../../../core/dist/task-list-format.js");
-        expect(existsSync(distTaskListFormat)).toBe(true);
 
         const store = new TaskStore(tmpDir);
         await store.init();

packages/core/src/__test-utils__/__tests__/core-dist.test.ts

@@ -0,0 +1,46 @@
+import { mkdirSync, writeFileSync } from "node:fs";
+import { join } from "node:path";
+import { describe, expect, it } from "vitest";
+import { hasBuiltCoreDistBarrel, requiredCoreDistFiles, tempWorkspace } from "../workspace.js";
+
+describe("hasBuiltCoreDistBarrel", () => {
+  function makeDistDir() {
+    const root = tempWorkspace("fusion-core-dist-predicate-");
+    const distDir = join(root, "dist");
+    mkdirSync(distDir, { recursive: true });
+    return distDir;
+  }
+
+  function touchDistFile(distDir: string, file: (typeof requiredCoreDistFiles)[number]) {
+    writeFileSync(join(distDir, file), "export {};\n");
+  }
+
+  it("returns false when the dist barrel is absent", () => {
+    const distDir = makeDistDir();
+
+    expect(hasBuiltCoreDistBarrel(distDir)).toBe(false);
+  });
+
+  it("returns false when index.js exists without task-list-format.js", () => {
+    const distDir = makeDistDir();
+    touchDistFile(distDir, "index.js");
+
+    expect(hasBuiltCoreDistBarrel(distDir)).toBe(false);
+  });
+
+  it("returns false when task-list-format.js exists without index.js", () => {
+    const distDir = makeDistDir();
+    touchDistFile(distDir, "task-list-format.js");
+
+    expect(hasBuiltCoreDistBarrel(distDir)).toBe(false);
+  });
+
+  it("returns true only when all required core dist files exist", () => {
+    const distDir = makeDistDir();
+    for (const file of requiredCoreDistFiles) {
+      touchDistFile(distDir, file);
+    }
+
+    expect(hasBuiltCoreDistBarrel(distDir)).toBe(true);
+  });
+});

packages/core/src/__test-utils__/workspace.ts

@@ -16,6 +16,17 @@ import { join, resolve } from "node:path";
 import { afterEach } from "vitest";
 import { assertOutsideRealFusionPath } from "../test-safety.js";
 
+/**
+ * FNXC:CoreTests 2026-06-18-01:30:
+ * FN-6627 requires built-dist-barrel regression guards to skip cleanly when @fusion/core/dist is absent or partial, and to run with full FN-6515/FN-6535 signal only when the same artifacts loaded by the test are present.
+ * Keep new dist-dependent guards on this predicate instead of checking index.js separately from task-list-format.js body assertions.
+ */
+export const requiredCoreDistFiles = ["index.js", "task-list-format.js"] as const;
+
+export function hasBuiltCoreDistBarrel(distDir: string): boolean {
+  return requiredCoreDistFiles.every((file) => existsSync(resolve(distDir, file)));
+}
+
 export function assertOutsideRealFusion(path: string, context = "operation"): void {
   assertOutsideRealFusionPath(path, context);
 }

packages/core/src/__tests__/task-list-format.test.ts

@@ -1,4 +1,3 @@
-import { existsSync } from "node:fs";
 import { dirname, resolve } from "node:path";
 import { fileURLToPath, pathToFileURL } from "node:url";
 import { beforeAll, describe, expect, it } from "vitest";
@@ -7,6 +6,7 @@ import {
   MAX_TASK_LIST_TEXT_CHARS as SOURCE_BARREL_MAX_TASK_LIST_TEXT_CHARS,
   formatTaskListText as sourceBarrelFormatTaskListText,
 } from "../index.js";
+import { hasBuiltCoreDistBarrel } from "@fusion/test-utils";
 import { clampTaskListText, formatTaskListText, MAX_TASK_LIST_TEXT_CHARS } from "../task-list-format.js";
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
@@ -78,18 +78,21 @@ function executeRuntimeTaskList(
  * FN-6535 requires this guard to execute a fn_task_list-shaped runtime call through the built dist module, not just assert the barrel types. The recurring crash was a post-FN-6492 tool call resolving @fusion/core through exports.import to stale dist, so the regression must fail when that dist omits the helper.
  */
 describe("@fusion/core dist barrel export wiring (FN-6515/FN-6535)", () => {
-  const distIndex = resolve(__dirname, "../../dist/index.js");
-  const distTaskListFormat = resolve(__dirname, "../../dist/task-list-format.js");
+  const distDir = resolve(__dirname, "../../dist");
+  const hasCompleteDistBarrel = hasBuiltCoreDistBarrel(distDir);
+  const distIndex = resolve(distDir, "index.js");
   let builtDistCore: RuntimeCoreTaskListModule | undefined;
 
   /*
   FNXC:CoreTests 2026-06-17-13:40:
   FN-6591 requires the FN-6515/FN-6535 dist-barrel guard to settle under broad @fusion/core suite load without timeout, retry, or worker appeasement.
   Load the built dist barrel once for every dist assertion so heartbeat fn_task_list coverage still exercises the real runtime export path while avoiding duplicate dynamic-import pressure in the timed test bodies.
+
+  FNXC:CoreTests 2026-06-18-01:35:
+  FN-6627 requires this guard to skip when the built @fusion/core dist barrel is absent or partial, because the runtime import path depends on both index.js and task-list-format.js.
   */
   beforeAll(async () => {
-    if (!existsSync(distIndex)) return;
-    expect(existsSync(distTaskListFormat)).toBe(true);
+    if (!hasCompleteDistBarrel) return;
     builtDistCore = await import(pathToFileURL(distIndex).href) as RuntimeCoreTaskListModule;
   });
 
@@ -99,7 +102,7 @@ describe("@fusion/core dist barrel export wiring (FN-6515/FN-6535)", () => {
     expect(typeof SOURCE_BARREL_MAX_TASK_LIST_TEXT_CHARS).toBe("number");
   });
 
-  it.skipIf(!existsSync(distIndex))("re-exports task-list formatting helpers from the built dist barrel", () => {
+  it.skipIf(!hasCompleteDistBarrel)("re-exports task-list formatting helpers from the built dist barrel", () => {
     const mod = builtDistCore;
 
     expect(mod).toBeDefined();
@@ -108,7 +111,7 @@ describe("@fusion/core dist barrel export wiring (FN-6515/FN-6535)", () => {
     expect(typeof mod?.MAX_TASK_LIST_TEXT_CHARS).toBe("number");
   });
 
-  it.skipIf(!existsSync(distIndex))("executes the fn_task_list surface through the built dist core module", () => {
+  it.skipIf(!hasCompleteDistBarrel)("executes the fn_task_list surface through the built dist core module", () => {
     const mod = builtDistCore as RuntimeCoreTaskListModule;
     const todoAnchor: RuntimeTask = {
       id: "FN-001",