test(config): add config-get/set roundtrip and cross-workflow structural tests for use_worktrees

Add comprehensive test coverage for the workflow.use_worktrees config toggle:
- config-get returns false after setting to false (roundtrip verification)
- config-get errors with "Key not found" when not set (validates workflow
  fallback behavior where `|| echo "true"` provides the default)
- config-get returns true after setting to true
- Toggle back and forth works correctly
- Structural tests verify USE_WORKTREES is wired into quick.md,
  diagnose-issues.md, execute-plan.md, planning-config.md, and config.cjs

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/execute-phase-wave.test.cjs

@@ -122,3 +122,63 @@ describe('execute-phase docs: user-facing wave flag', () => {
     );
   });
 });
+
+describe('use_worktrees config: cross-workflow structural coverage', () => {
+  const QUICK_PATH = path.join(__dirname, '..', 'get-shit-done', 'workflows', 'quick.md');
+  const DIAGNOSE_PATH = path.join(__dirname, '..', 'get-shit-done', 'workflows', 'diagnose-issues.md');
+  const EXECUTE_PLAN_PATH = path.join(__dirname, '..', 'get-shit-done', 'workflows', 'execute-plan.md');
+  const PLANNING_CONFIG_PATH = path.join(__dirname, '..', 'get-shit-done', 'references', 'planning-config.md');
+  const CONFIG_CJS_PATH = path.join(__dirname, '..', 'get-shit-done', 'bin', 'lib', 'config.cjs');
+
+  test('quick workflow reads USE_WORKTREES from config', () => {
+    const content = fs.readFileSync(QUICK_PATH, 'utf-8');
+    assert.ok(
+      content.includes('config-get workflow.use_worktrees'),
+      'quick.md should read use_worktrees from config'
+    );
+    assert.ok(
+      content.includes('USE_WORKTREES'),
+      'quick.md should reference USE_WORKTREES variable'
+    );
+  });
+
+  test('diagnose-issues workflow reads USE_WORKTREES from config', () => {
+    const content = fs.readFileSync(DIAGNOSE_PATH, 'utf-8');
+    assert.ok(
+      content.includes('config-get workflow.use_worktrees'),
+      'diagnose-issues.md should read use_worktrees from config'
+    );
+    assert.ok(
+      content.includes('USE_WORKTREES'),
+      'diagnose-issues.md should reference USE_WORKTREES variable'
+    );
+  });
+
+  test('execute-plan workflow references use_worktrees config', () => {
+    const content = fs.readFileSync(EXECUTE_PLAN_PATH, 'utf-8');
+    assert.ok(
+      content.includes('workflow.use_worktrees'),
+      'execute-plan.md should reference workflow.use_worktrees'
+    );
+  });
+
+  test('planning-config reference documents use_worktrees', () => {
+    const content = fs.readFileSync(PLANNING_CONFIG_PATH, 'utf-8');
+    assert.ok(
+      content.includes('workflow.use_worktrees'),
+      'planning-config.md should document workflow.use_worktrees'
+    );
+    assert.ok(
+      content.includes('worktree'),
+      'planning-config.md should describe worktree behavior'
+    );
+  });
+
+  test('config.cjs includes workflow.use_worktrees in VALID_CONFIG_KEYS', () => {
+    const content = fs.readFileSync(CONFIG_CJS_PATH, 'utf-8');
+    assert.ok(
+      content.includes("'workflow.use_worktrees'"),
+      'config.cjs VALID_CONFIG_KEYS should include workflow.use_worktrees'
+    );
+  });
+});