fix(coach): keep the chart on a table shown again

Asking for an earlier table "as a chart" went through show_result, which
builds the requested view, but collecting the turn's tables then reset
every chart to null and only derived a new one for fresh tables. The table
came back without its chart. A table shown again now keeps the view it was
given.

src/lib/ai/coach/results/__tests__/project.test.ts

@@ -65,6 +65,34 @@ describe("projectResults", () => {
     expect(out.every((t) => !t.displayed && t.chart === null)).toBe(true);
   });
 
+  it("keeps the view a table shown again was given", () => {
+    const shownAgain = {
+      ...table("r1", 5),
+      reusedFrom: { messageId: "m-a1", ref: "r2" },
+    };
+    const [asChart, asTable] = projectResults({
+      locale: "en",
+      calls: [
+        { name: "show_result", result: { present: true, table: shownAgain } },
+        {
+          name: "show_result",
+          result: {
+            present: true,
+            table: { ...shownAgain, ref: "r2", chart: null, chartKind: null },
+          },
+        },
+      ],
+    });
+    expect(asChart.chart).toEqual({
+      kind: "line",
+      x: "day",
+      series: ["value"],
+    });
+    expect(asChart.chartKind).toBe("line");
+    expect(asTable.chart).toBeNull();
+    expect(asTable.chartKind).toBeNull();
+  });
+
   it("trims a table to the row ceiling and says so", () => {
     const [out] = projectResults({
       locale: "en",

src/lib/ai/coach/results/project.ts

@@ -37,7 +37,7 @@ function refNumber(ref: string): number {
 /**
  * Tables for this turn, in ref order (`r1`..), at most six, each trimmed to
  * `RESULT_TABLE_MAX_ROWS`. `chart` and `chartKind` are left for
- * `deriveChartSpec` to fill.
+ * `deriveChartSpec` to fill, except on a table shown again.
  */
 export function projectResults(args: {
   calls: SettledToolCall[];
@@ -56,8 +56,12 @@ export function projectResults(args: {
       rowCount: Math.max(table.rowCount, rows.length),
       truncated: table.truncated || rows.length < table.rows.length,
       displayed: false,
-      chart: null,
-      chartKind: null,
+      // A table shown again keeps the view `show_result` chose for it (a
+      // chart, a histogram, or none); `withChart` leaves it as it is. Every
+      // other table gets its chart from `deriveChartSpec`.
+      ...(table.reusedFrom
+        ? { chart: table.chart, chartKind: table.chartKind }
+        : { chart: null, chartKind: null }),
     });
   }
   return tables