Fix every real lint finding and drop degenerate splice fragments

ingestion/tests/test_extract_page_map.py

@@ -0,0 +1,27 @@
+from ingestion.extract.page_map import pick_folio
+
+
+def test_single_candidate_is_the_folio():
+    assert pick_folio([("101", 10.0)]) == 101
+
+
+def test_no_candidates_is_unrecoverable():
+    assert pick_folio([]) is None
+
+
+def test_confirmed_riboflavin_subscript_conflict_resolved_by_size():
+    # exact (text, size) pairs read from physical page 1243's header band:
+    # the real folio "1244" (size 10.0, matching the rest of the running
+    # header) and the "2" subscript from "Vitamin B2" (size 5.83), which
+    # happens to fall in the same y<60 header band because the RIBOFLAVIN
+    # title sits high on the page — see module docstring. Silently dropped
+    # the whole monograph before this fix, confirmed via a whole-book
+    # `cli validate` run and by rendering the page to an image.
+    candidates = [("1244", 10.0), ("2", 5.83)]
+    assert pick_folio(candidates) == 1244
+
+
+def test_genuine_same_size_conflict_still_returns_none():
+    # two same-size digit-only candidates: real ambiguity, must not guess
+    candidates = [("101", 10.0), ("205", 10.0)]
+    assert pick_folio(candidates) is None