fix(review,autoplan): require explicit run_in_background: false on specialist agents

Claude Code v2.1.198 made subagents run in the background by default, which
inverted the old "do not use the flag" guidance: review-army specialists and
autoplan dual voices silently launched in the background and the merge step
could proceed before they completed — regressing the #497 fix. The generated
guidance now instructs an explicit run_in_background: false, and a static
tripwire fails the free suite if the inert inverted phrasing ever returns to
any generated SKILL.md.

Fixes #2440.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

test/fixtures/golden/factory-ship-SKILL.md

@@ -2177,7 +2177,7 @@ CHECKLIST:
 
 **Subagent configuration:**
 - Use `subagent_type: "general-purpose"`
-- Do NOT use `run_in_background` — all specialists must complete before merge
+- Pass `run_in_background: false` on every specialist Agent call — subagents run in the BACKGROUND by default since Claude Code v2.1.198, and all specialists must complete before merge. (Merely omitting the flag no longer produces a foreground run; it must be explicitly false.)
 - If any specialist subagent fails or times out, log the failure and continue with results from successful specialists. Specialists are additive — partial results are better than no results.
 
 ---

test/run-in-background-guidance.test.ts

@@ -0,0 +1,66 @@
+import { describe, test, expect } from 'bun:test';
+import * as fs from 'fs';
+import * as path from 'path';
+
+// Regression guard for #2440 (which itself regressed the #497 fix).
+//
+// Claude Code v2.1.198 made subagents run in the BACKGROUND by default.
+// Guidance written before that ("do NOT use run_in_background") stopped
+// producing a foreground run — the review army and autoplan dual-voice
+// steps silently launched specialists in the background and merged before
+// they completed. The only guidance that works post-2.1.198 is an explicit
+// `run_in_background: false` on the Agent call.
+//
+// This tripwire pins the corrected phrasing in the generated skill output
+// and fails if the inverted form ever comes back through a template or
+// resolver edit.
+
+const ROOT = path.resolve(import.meta.dir, '..');
+
+const GENERATED_WITH_GUIDANCE = ['review/SKILL.md', 'autoplan/SKILL.md'];
+
+// The inverted, post-2.1.198-inert phrasings. Checked across every generated
+// SKILL.md so the regression can't migrate to another skill unnoticed.
+const INVERTED = /do not use\s+`?run_in_background`?/i;
+
+function allGeneratedSkillFiles(): string[] {
+  const out: string[] = [];
+  for (const entry of fs.readdirSync(ROOT, { withFileTypes: true })) {
+    if (!entry.isDirectory() || entry.name.startsWith('.') || entry.name === 'node_modules') continue;
+    const p = path.join(ROOT, entry.name, 'SKILL.md');
+    if (fs.existsSync(p)) out.push(p);
+    // Generated on-demand section files (e.g. ship/sections/review-army.md)
+    // carry the same resolver output as SKILL.md bodies — scan them too.
+    const sections = path.join(ROOT, entry.name, 'sections');
+    if (fs.existsSync(sections)) {
+      for (const f of fs.readdirSync(sections)) {
+        if (f.endsWith('.md')) out.push(path.join(sections, f));
+      }
+    }
+  }
+  const rootSkill = path.join(ROOT, 'SKILL.md');
+  if (fs.existsSync(rootSkill)) out.push(rootSkill);
+  return out;
+}
+
+describe('run_in_background guidance (#2440)', () => {
+  test('foreground-required skills instruct run_in_background: false explicitly', () => {
+    for (const rel of GENERATED_WITH_GUIDANCE) {
+      const content = fs.readFileSync(path.join(ROOT, rel), 'utf-8');
+      expect(content).toContain('run_in_background: false');
+    }
+  });
+
+  test('the inverted "do NOT use run_in_background" phrasing never comes back', () => {
+    for (const file of allGeneratedSkillFiles()) {
+      const content = fs.readFileSync(file, 'utf-8');
+      if (INVERTED.test(content)) {
+        throw new Error(
+          `${path.relative(ROOT, file)} contains the inverted run_in_background guidance — ` +
+          'since Claude Code v2.1.198 subagents default to background, so "do not use" is inert; ' +
+          'instruct `run_in_background: false` instead (see #2440).',
+        );
+      }
+    }
+  });
+});