feat(format): case_collapse uses line_width via Doc-IR

pkg/format/dml.go

@@ -861,10 +861,6 @@ func alignSetItems(texts []string) []string {
 	return out
 }
 
-// caseCollapseWidth is the inline-length threshold under which case_collapse
-// keeps a CASE expression on one line even when case_when_wrap is set.
-const caseCollapseWidth = 60
-
 // dmlIsCaseStart reports whether t is a CASE keyword token.
 func dmlIsCaseStart(t cst.Tok) bool {
 	return t.Tok.Kind == lexer.Ident && lowerASCII(t.Tok.Text) == "case"
@@ -1001,10 +997,12 @@ func dmlFormatCase(toks []cst.Tok, st config.Style) string {
 	if !st.CaseWhenWrap {
 		return inline
 	}
-	if st.CaseCollapse && len(inline) <= caseCollapseWidth {
-		return inline
+	wrapped := dmlCaseWrapped(caseKw, operand, whens, elseKw, elseText, haveElse, endKw, st)
+	if st.CaseCollapse {
+		// Collapse when the one-line form fits in line_width.
+		return Render(Group(IfBreak(Text(wrapped), Text(inline))), st.LineWidth, st.Indent, st.Newline)
 	}
-	return dmlCaseWrapped(caseKw, operand, whens, elseKw, elseText, haveElse, endKw, st)
+	return wrapped
 }
 
 // dmlCaseInline renders a CASE expression on a single line.