feat(travel): 交通费行按实际乘车日填开始/结束日期（联机实测控件 #ksrq/#jsrq）

用户第 4 条：交通费行的日期由页面按出差起止自动带出，cost=1 分支不填日期，于是「6-02 出发、
6-05 才坐车」这种情况报销日期是错的。要按乘车日必须先知道控件 id，所以做了一次联机探测：
登录 → new_form(travel) → fill(basic) 落草稿 → actor 里打开明细、点 #insertDetail、选 cost=1、
dump 可见 input → 截图；探完按守卫删草稿（唯一命中+未提交+当日制单，bill_no 202610030261，复查 0 命中）。

探测结果：交通费行日期控件 #ksrq（expenPwTraveldetail.STARTDATE）/ #jsrq（OVERDATE），
页面已按出差起止预填（实测 2026-06-02 → 06-04）。

- add_travel_items 的 cost=1 分支用 transport_fee[].start_date/end_date 覆盖 #ksrq/#jsrq
- 缺日期时保留页面带出的值并 log.warning，不静默按出差起止报销
- tests/test_travel_dates.py 两例：有乘车日则覆盖、缺日期不覆盖
- 文档：AGENTS 记下控件名与口径、操作指南 7.2 补一句、方案文档 §25 记探测方法与结论（含可复用的探测套路）

验证：pytest 全绿；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_travel_dates.py

@@ -0,0 +1,79 @@
+"""差旅明细：交通费行按实际乘车日填开始/结束日期（控件 #ksrq/#jsrq 为联机实测）。"""
+
+from typing import Any
+
+from src.infra.browser import travel
+
+
+class _Page:
+    def __init__(self) -> None:
+        self.fills: dict[str, str] = {}
+        self.selects: list[tuple[str, str]] = []
+        self.clicks: list[str] = []
+
+    def click(self, selector: str, timeout: int | None = None) -> None:
+        self.clicks.append(selector)
+
+    def select_option(self, selector: str, value: str) -> None:
+        self.selects.append((selector, value))
+
+    def fill(self, selector: str, value: str) -> None:
+        self.fills[selector] = value
+
+    def wait_for_timeout(self, ms: int) -> None:
+        pass
+
+
+class _Bot:
+    def __init__(self) -> None:
+        self.page = _Page()
+
+    def open_tab(self, name: str, timeout_ms: int = 20000) -> bool:
+        return True
+
+    def tab_ready(self, name: str) -> bool:
+        return True
+
+    def click_if_visible(self, selector: str, timeout_ms: int = 4000) -> bool:
+        return True
+
+    def _wait_for(self, selector: str, timeout: int | None = None) -> None:
+        pass
+
+    def _screenshot(self, name: str) -> str:
+        return ""
+
+
+def _transport(start: str, end: str) -> dict[str, Any]:
+    return {
+        "vehicle_type": "火车",
+        "start_date": start,
+        "end_date": end,
+        "departure_place": "阜阳",
+        "arrival_place": "合肥",
+        "amount": "233",
+        "bill_count": "2",
+        "remark": "两张高铁票",
+    }
+
+
+def test_transport_dates_use_ride_dates() -> None:
+    bot = _Bot()
+    travel.add_travel_items(
+        bot,  # type: ignore[arg-type]
+        {"transport_fee": [_transport("2026-06-05", "2026-06-05")], "hotel_fee": [], "conference_fee": []},
+    )
+    assert bot.page.fills["#ksrq"] == "2026-06-05"
+    assert bot.page.fills["#jsrq"] == "2026-06-05"
+    assert ("#jtgj", "01") in bot.page.selects  # 交通工具仍然照选
+    assert bot.page.fills["#ksdd"] == "阜阳" and bot.page.fills["#jsdd"] == "合肥"
+
+
+def test_missing_dates_keep_page_defaults() -> None:
+    bot = _Bot()
+    travel.add_travel_items(
+        bot,  # type: ignore[arg-type]
+        {"transport_fee": [_transport("", "")], "hotel_fee": [], "conference_fee": []},
+    )
+    assert "#ksrq" not in bot.page.fills and "#jsrq" not in bot.page.fills  # 不覆盖页面带出的出差起止
+    assert bot.page.fills["#ksdd"] == "阜阳"