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/runtime.py

@@ -26,7 +26,7 @@ from inbound_verify.domain import SITE_UNDELIVERED_FILE
 
 from inbound_verify import state_store
 from inbound_verify.sites import shunxin, baishi, zto, yunda, anneng
-from inbound_verify import expected_undelivered  # dispatch 的 compare 任务用
+from inbound_verify import compare  # dispatch 的 compare 任务用
 
 # 各网页站点首页 URL（单一来源，取自各站点模块 HOME_URL）
 SITES_CONFIG = {
@@ -444,7 +444,7 @@ def _site_undelivered_handler(site):
             (TASK_HANDLERS[(site, "actual")](ctx) is not False) if exp_ok else False
         )
         if exp_ok and act_ok:
-            return expected_undelivered.write_site_file(site)
+            return compare.write_site_file(site)
         stale = os.path.join(DOWNLOAD_DIR, SITE_UNDELIVERED_FILE.format(name=site))
         if os.path.exists(stale):
             os.remove(stale)
@@ -472,7 +472,7 @@ TASK_HANDLERS = {
     ("安能", "expected"): lambda ctx: anneng.anneng_expected_download(),
     ("安能", "actual"): lambda ctx: anneng.anneng_actual_download(),
     ("安能", "undelivered"): _site_undelivered_handler("安能"),
-    ("__compare__", "compare"): lambda ctx: (expected_undelivered.main() or True),
+    ("__compare__", "compare"): lambda ctx: (compare.main() or True),
 }