Pure parser in core/src/bible/refs: OSIS refs and ranges, TSK abbreviations
and relative forms, refs the versification lacks kept and marked.

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

@@ -0,0 +43,4 @@
+
+    fn osis_item(item: &str) -> Option<Cite> {
+        let item = item.split_once(':').map_or(item, |(_, r)| r);
+        let item = item.split(['!', '@']).next()?;

@@ -0,0 +15,4 @@
+impl Piece {
+    fn parse(s: &str) -> Option<Piece> {
+        // `16a` and `16ff` are verse 16.
+        let s = s.trim().trim_end_matches(|c: char| c.is_alphabetic() || c == '.' || c.is_whitespace());

@@ -0,0 +67,4 @@
+        let starts_book = |s: &str| {
+            let s = s.trim_start();
+            let rest = s.trim_start_matches(|c: char| c.is_ascii_digit());
+            !s.is_empty() && rest.trim_start().starts_with(|c: char| c.is_alphabetic())

@@ -0,0 +87,4 @@
+        let mut chapter = if name.is_empty() {
+            self.chapter
+        } else {
+            let Some(book) = books::osis(name) else {

@@ -0,0 +104,4 @@
+            match Piece::parse(text).and_then(|p| Self::cite(book, chapter, &p)) {
+                Some(cite) => {
+                    // After a whole chapter, a bare number is another chapter.
+                    chapter = cite.last.verse.and(cite.last.chapter);

@@ -0,0 +76,4 @@
+            }
+            // `18a`, `9ff` and `18a-20` are verses with a suffix: a piece that
+            // starts with digits is a book only when it names one (`2 Co 5`).
+            rest.len() == s.len() || books::osis(split_book(s).0).is_some()