feat(normalizer): overrides loader + xlsx/csv writers

Recovered from an entangled commit: these files were correct but had been
bundled into an unrelated reader-dashboard commit by a concurrent session.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tools/import-normalizer/overrides.py

@@ -0,0 +1,21 @@
+"""Load human-supplied corrections. Missing files are not an error."""
+import csv
+from pathlib import Path
+
+
+def load_overrides(dates_path: Path, names_path: Path):
+    date_overrides: dict[str, tuple[str, str]] = {}
+    name_overrides: dict[str, str] = {}
+    if Path(dates_path).exists():
+        with open(dates_path, encoding="utf-8", newline="") as f:
+            for row in csv.DictReader(f):
+                raw = (row.get("raw") or "").strip()
+                if raw:
+                    date_overrides[raw] = ((row.get("iso") or "").strip(), (row.get("precision") or "UNKNOWN").strip())
+    if Path(names_path).exists():
+        with open(names_path, encoding="utf-8", newline="") as f:
+            for row in csv.DictReader(f):
+                raw = (row.get("raw") or "").strip()
+                if raw:
+                    name_overrides[raw] = (row.get("person_id") or "").strip()
+    return date_overrides, name_overrides