feat: report_builder uses weighted means; ReportData gains weighted_score_mean

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

webapp/services/run_reader.py

@@ -64,6 +64,27 @@ def _read_metrics_from_snapshot(run_dir: Path) -> list[str]:
     return []
 
 
+def _read_weights_from_snapshot(run_dir: Path) -> tuple[dict[str, float], dict[str, float]]:
+    """Read metric_weights and doc_weights from a scenario snapshot if present.
+
+    Returns a (metric_weights, doc_weights) tuple of plain dicts.
+    Both default to empty dicts when the snapshot is absent or lacks the fields.
+    """
+    snapshot = run_dir / "scenario.snapshot.yaml"
+    if not snapshot.is_file():
+        return {}, {}
+    try:
+        payload = yaml.safe_load(snapshot.read_text(encoding="utf-8")) or {}
+    except (OSError, yaml.YAMLError):
+        return {}, {}
+    mw = payload.get("metric_weights") or {}
+    dw = payload.get("doc_weights") or {}
+    return (
+        {str(k): float(v) for k, v in mw.items() if isinstance(v, (int, float))},
+        {str(k): float(v) for k, v in dw.items() if isinstance(v, (int, float))},
+    )
+
+
 def discover_run_dirs(extra_roots: list[Path] | None = None) -> list[Path]:
     """Find every run directory (one that contains metadata.json) under the roots."""
     run_dirs: list[Path] = []
@@ -159,6 +180,8 @@ NON_METRIC_COLUMNS = {
     "source_chunk_ids",
     "review_status",
     "review_notes",
+    "weighted_score",
+    "sample_weight",
 }