refactor: rename expected_undelivered to compare

git mv expected_undelivered.py -> compare.py; update the 3 importers (store/runtime/router) to import compare. All public names (main, write_site_file, _read_business_dates) unchanged. Also add the Tier 2 plan doc.

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

inbound_verify/cli/router.py

@@ -24,14 +24,14 @@ from inbound_verify import state_store
 
 # 各站点模块（自动化测试 + 比对用；任务派发在 runtime）
 from inbound_verify.sites import shunxin, baishi, zto, yunda, anneng
-from inbound_verify import expected_undelivered
+from inbound_verify import compare
 
 
 def run_undelivered_compare():
-    """应到未到比对（全站点）：调用 expected_undelivered，读 downloads/ 下的应到/实到
+    """应到未到比对（全站点）：调用 compare，读 downloads/ 下的应到/实到
     数据，生成 output/应到未到数据.xlsx（汇总报表 + 各站明细）。"""
     print("\n▶ 开始执行【应到未到比对（全站点）】任务 ...")
-    expected_undelivered.main()
+    compare.main()
 
 
 # ====================================================================