fix(l2): let Step 3 switch between risk events (for #21)

frontend/components/risk_dashboard.py

@@ -442,12 +442,14 @@ def render_response_execution(
     if "resp_active_event_sel" not in st.session_state:
         st.session_state["resp_active_event_sel"] = 0
 
-    if "active_risk_event_id" in st.session_state:
-        target_id = st.session_state["active_risk_event_id"]
-        if target_id in event_ids:
-            new_idx = event_ids.index(target_id)
-            # 🧪 關鍵修正：若有外部跳轉指令，手動強制覆寫 selectbox 的內部 state
-            st.session_state["resp_active_event_sel"] = new_idx
+    # 外部跳轉（卡片「查看分析」）是一次性指令：取出後就清掉。
+    # 原本用 active_risk_event_id（＝目前選取的鏡像）來強制 selectbox，導致
+    # 使用者在下拉選另一個事件時，rerun 又被拉回上一個，永遠切不過去。
+    target_id = st.session_state.pop("jump_to_risk_event_id", None)
+    if target_id is not None and target_id in event_ids:   # event_ids[0] 是佔位的 None
+        st.session_state["resp_active_event_sel"] = event_ids.index(target_id)
+    elif st.session_state["resp_active_event_sel"] >= len(event_options):
+        st.session_state["resp_active_event_sel"] = 0   # 事件被刪除後索引失效
 
     selected_idx = st.selectbox(
         "選擇要分析與執行的風險事件", 

frontend/components/supply_map.py

@@ -205,7 +205,8 @@ def render_risk_shortcuts(key: str, heatmap_rows=None, *, actor: str):
 
             if btn_state == "view":
                 if st.button("📊 查看分析", key=f"{key}_quick_anal_{region_key}_{i}", use_container_width=True, type="secondary"):
-                    st.session_state["active_risk_event_id"] = found_ev["id"]
+                    # 一次性的跳轉指令；active_risk_event_id 只反映目前選取，不用來強制 selectbox
+                    st.session_state["jump_to_risk_event_id"] = found_ev["id"]
                     st.rerun()
             elif btn_state == "update":
                 if st.button("🔄 更新應變建議", key=f"{key}_upd_{region_key}", use_container_width=True, type="primary"):

tests/test_step3_event_switch.py

@@ -0,0 +1,38 @@
+"""
+tests/test_step3_event_switch.py
+步驟 3 事件下拉：有多個正式事件時，使用者必須能從 A 切到 B。
+
+原本卡片「查看分析」和 selectbox 都寫 active_risk_event_id，而 rerun 時又用它
+強制覆寫 selectbox，於是選了 B 也會被拉回 A。跳轉改成一次性的 jump_to_risk_event_id。
+"""
+
+from __future__ import annotations
+
+import ast
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[1]
+
+
+def _assigned_keys(tree):
+    keys = set()
+    for node in ast.walk(tree):
+        if isinstance(node, ast.Assign):
+            for target in node.targets:
+                if (isinstance(target, ast.Subscript)
+                        and isinstance(target.value, ast.Attribute)
+                        and target.value.attr == "session_state"
+                        and isinstance(target.slice, ast.Constant)):
+                    keys.add(target.slice.value)
+    return keys
+
+
+def test_card_jump_uses_one_shot_key_and_step3_consumes_it():
+    supply_map = ast.parse((ROOT / "frontend/components/supply_map.py").read_text(encoding="utf-8"))
+    dashboard_src = (ROOT / "frontend/components/risk_dashboard.py").read_text(encoding="utf-8")
+
+    assert "jump_to_risk_event_id" in _assigned_keys(supply_map)
+    assert "active_risk_event_id" not in _assigned_keys(supply_map)
+    # 步驟 3 取出即清除，且不再拿 active_risk_event_id 去覆寫 selectbox
+    assert 'st.session_state.pop("jump_to_risk_event_id"' in dashboard_src
+    assert 'target_id = st.session_state["active_risk_event_id"]' not in dashboard_src