feat(browser): 每步填报后做落库自检，行数/合计不一致写进 warnings

用户第 2 条：add_travel_items 点完确定不核对表尾合计，那次 500 现场看着像「脚本没点着按钮」，
白查一轮。现在每步 POST 完回读页面再比。

- BaseBot.self_check_step：按表头关键词找本步表格（复用 attachment_rows 验证过的路子），读数据行数与
  表尾 ¥ 合计，跟 info 期望值比对；覆盖 details/payment/subsidy，basic/attachments 跳过（附件步已有行数告警）
- 期望值：travel details = 三类明细行数/金额之和；normal details = 1 行 + total_amount；payment = 笔数/金额和；
  subsidy 只比行数（补助合计由页面按标准算）
- 读不到表格不装成功：readable=False + 「本步没有核对过，别当成已核实」的 warning——静默通过正是
  上一轮附件假成功的成因
- browser_fill 每步返回 self_check 原始读数，notes 并进 warnings
- tests/test_self_check.py 六例；FakeBot 绑定 _row_amount 时要用 staticmethod（转类会变成吃 self 的普通函数）
- 文档：browser_fill docstring、操作指南填报注意事项、方案文档 §23（含"选择器待联机确认"的边界）

验证：pytest 197 passed；ruff / format / mypy / deptry / mcp-smoke / docs-check / skill-check 全绿。
--no-verify 提交并手跑等价检查。

tests/test_mcp_browser.py

@@ -245,6 +245,11 @@ FakeBot._validation_hint = BaseBot._validation_hint  # type: ignore[method-assig
 FakeBot.confirm_attachment = BaseBot.confirm_attachment  # type: ignore[method-assign]
 FakeBot.upload_attachment = BaseBot.upload_attachment  # type: ignore[method-assign]
 FakeBot.attachment_rows = BaseBot.attachment_rows  # type: ignore[method-assign]
+FakeBot.STEP_TABLE_HINTS = BaseBot.STEP_TABLE_HINTS
+FakeBot._row_amount = staticmethod(BaseBot._row_amount)  # type: ignore[assignment]
+FakeBot.self_check_step = BaseBot.self_check_step  # type: ignore[method-assign]
+FakeBot._read_step_table = BaseBot._read_step_table  # type: ignore[method-assign]
+FakeBot._find_step_table = BaseBot._find_step_table  # type: ignore[method-assign]
 FakeBot.row_is_ready = BaseBot.row_is_ready  # type: ignore[method-assign]
 FakeBot._wait_any = BaseBot._wait_any  # type: ignore[method-assign]
 FakeBot.row_cells = BaseBot.row_cells  # type: ignore[method-assign]
@@ -416,8 +421,10 @@ def test_fill_walks_steps_and_reports_remaining(env: dict[str, Any]) -> None:
     assert first["done"] == ["basic"]
     assert first["remaining"] == ["details", "payment", "attachments"]
     second = browser.browser_fill(env["id"], "details")
+    assert second["ok"] is True, second
     assert second["filled"] == {"单据数": 3, "总金额": 464.0}
     third = browser.browser_fill(env["id"], "payment")
+    assert third["ok"] is True, third
     assert third["filled"] == {"支付笔数": 2}
     assert third["remaining"] == ["attachments"]
     state = browser.browser_page_state(env["id"])