fix(agent): describe typed historical comparison charts

Use time_comparison for current curves and historical point sets. Document shared time slots and aligned real sample timestamps; synchronize the generated chart contracts.

tests/frontendAction/command.test.ts

@@ -35,9 +35,10 @@ describe("unified view commands", () => {
   });
   it("passes aligned historical scatter points through native and publication contracts", () => {
     const command = { action: "open_chart", chart_id: "pressure-comparison", evidence_refs: ["E1"], chart: {
-      title: "压力七天对比", chart_type: "line", y_axis_name: "压力（m）",
+      title: "压力七天对比", chart_type: "time_comparison", y_axis_name: "压力（m）",
       x_data: ["19:30", "19:45", "20:00"], series: [
-        { name: "当前", type: "line", data: [32, null, 31] },
+        { name: "当前", type: "line", data: [32, null, 31],
+          sample_times: ["2026-06-14T19:30:00+08:00", null, "2026-06-14T20:00:00+08:00"] },
         { name: "前一天", type: "scatter", data: [null, 32, 33],
           sample_times: [null, "2026-06-13T19:45:00+08:00", "2026-06-13T20:00:00+08:00"] },
       ],