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

README.md

@@ -76,6 +76,7 @@ pgtidy config   # print resolved config
 - Leading-comma lists (SELECT columns, function params)
 - Function params one-per-line; `LANGUAGE`, `SECURITY`, volatility each on own line
 - PL/pgSQL: `DECLARE` block vars 2-space indented; `BEGIN`/`END` at body level
+- Procedural languages: bodies in `pl*` languages other than `plpgsql` (e.g. `plpython3u`, `plperl`), `c` and `internal` are left verbatim; `plpgsql` and `sql` bodies are formatted, and the function header is always formatted
 - Spaces around binary operators (`=`, `<>`, `||`, `:=`); no space before `(` or around `::`, `->`, `->>`
 
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