bindings: the footnote signal, which book-pipeline still had its own copy of

`looks_like_footnote_citations` is the function chunkmd's `looks_like_citations`
was ported from, and book-pipeline was still running the Python original at
four call sites. Bound on all four surfaces so it can stop.

Checked against the Python over 34,458 chunks of the live corpus: no
disagreement.

crates/bindings/python/catena/__init__.py

@@ -19,6 +19,7 @@ from ._catena import (
     find_citations,
     fuse_hits,
     identify,
+    looks_like_footnote_citations,
     merge_citation_reply,
     pack_cues,
     parse_identifier,
@@ -38,6 +39,7 @@ __all__ = [
     "find_citations",
     "fuse_hits",
     "identify",
+    "looks_like_footnote_citations",
     "merge_citation_reply",
     "pack_cues",
     "parse_identifier",

crates/bindings/python/catena/__init__.pyi

@@ -38,6 +38,7 @@ def fuse_hits(
 ) -> list[dict[str, Any]]: ...
 def identify(name: str, data: bytes) -> dict[str, Any]: ...
 def find_citations(text: str) -> list[dict[str, Any]]: ...
+def looks_like_footnote_citations(text: str) -> bool: ...
 def citation_prompt(references: Iterable[Mapping[str, Any]]) -> str | None: ...
 def merge_citation_reply(
     references: Iterable[Mapping[str, Any]], reply: str