test: add worktree requirement test for subagent-driven-development

Add Test 8 to verify that using-git-worktrees is mentioned as a required
skill for subagent-driven-development. This test will initially fail per
TDD approach - the skill file needs to be updated to pass this test.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/claude-code/test-subagent-driven-development.sh

@@ -136,4 +136,17 @@ fi
 
 echo ""
 
+# Test 8: Verify worktree requirement
+echo "Test 8: Worktree requirement..."
+
+output=$(run_claude "What workflow skills are required before using subagent-driven-development? List any prerequisites or required skills." 30)
+
+if assert_contains "$output" "using-git-worktrees\|worktree" "Mentions worktree requirement"; then
+    : # pass
+else
+    exit 1
+fi
+
+echo ""
+
 echo "=== All subagent-driven-development skill tests passed ==="