[NOTICKET] fix(report): no default chart for descriptive evidence

- Since 0e64f6ba a descriptive answer's report evidence is its statistics
table (column, count, mean, median, std, min, max).
- analyze_descriptive draws no chart, so _default_chart built one from the
first measure, `count`: "Count by column" with identical bars (1080 x 4 on
the test-demo Q13 record).
- The other statistics mix units (PA in %, MTBS/MTTR in hours), so no single
bar chart reads right.
- _default_chart now returns None when the record ran analyze_descriptive;
the statistics table stays, rankings keep their default chart.
- Reported by Rifqi in the review of 3 Nov.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/agents/report/anchored.py

@@ -785,6 +785,15 @@ def _default_chart(info: RecordInfo, lang: str) -> dict | None:
     """
     if not info.evidence_raw:
         return None
+    # A descriptive table's first measure is `count`, equal for every column: the
+    # default bar was "Count by column" with identical bars (review 2026-11-03). Its
+    # other stats mix units (% vs hours), so no single bar reads right — table only.
+    if any(
+        o.tool == "analyze_descriptive"
+        for r in info.record.results_snapshot.values()
+        for o in r.outputs
+    ):
+        return None
     cols, rows = info.evidence_raw
     if len(rows) < 2:
         return None