feat(format): skip non-plpgsql bodies; keep literals and embedded code safe

- Only restyle bodies for plpgsql/sql; skip pl* (plpython3u, plperl, ...), c and internal
- Keep LANGUAGE clause on DO blocks
- Carry multi-line string and dollar-quoted literals verbatim in bodies and DML
- Format dollar-quoted literals that contain code (declare/begin/select/...), never format() templates
- Fix code joined onto -- comments, early flush after raise exception, dropped comment before BEGIN
- Regenerate test_mm_proc golden; document in README, plan, todo

pkg/format/dml.go

@@ -490,6 +490,12 @@ func dmlWrapSubquery(inner []cst.Tok, st config.Style) string {
 	return b.String()
 }
 
+// litNL stands in for a newline inside a multi-line string literal while DML
+// text is assembled; formatDML's caller restores it (see restoreLiteralNewlines).
+const litNL = "\x00\x01"
+
+func restoreLiteralNewlines(s string) string { return strings.ReplaceAll(s, litNL, "\n") }
+
 // dmlInline renders toks on one line with keyword casing and proper spacing.
 // If toks[1:] contains comment trivia the function falls back to verbatimSpan
 // so no comment is lost. Subquery parens and CASE…END expressions embedded
@@ -548,7 +554,17 @@ func dmlInline(toks []cst.Tok, st config.Style) string {
 			prev = toks[i-1].Tok
 		}
 		nextIsLParen := i+1 < len(toks) && toks[i+1].Tok.Kind == lexer.LParen
-		b.WriteString(caseTextCtx(t.Tok, prev, nextIsLParen, st))
+		txt := caseTextCtx(t.Tok, prev, nextIsLParen, st)
+		if t.Tok.Kind == lexer.DollarString {
+			txt = formatEmbedded(txt, st)
+		}
+		switch t.Tok.Kind {
+		case lexer.String, lexer.EscapeString, lexer.BitString, lexer.DollarString:
+			// Line breaks inside a literal are content: hide them from the
+			// line-based indent helpers that post-process this text.
+			txt = strings.ReplaceAll(txt, "\n", litNL)
+		}
+		b.WriteString(txt)
 		i++
 	}
 	return b.String()