feat(format): Doc-IR core, line_width (120) and where_wrap when_long

docs/todo.md

@@ -167,7 +167,7 @@ Legend: ✅ done · 🚧 in progress · ⬜ not started
   function call at the token level — formatted without space (known limitation).
 - Note: SQL keywords inside PL/pgSQL function bodies remain lowercase (matching
   the corpus golden files); casing is applied only to top-level DML.
-- _Still TODO: Wadler Doc-IR printer for width-aware wrapping of long lines._
+- ✅ Doc-IR core (`pkg/format/doc.go`: Text/Line/SoftLine/Group/Indent/IfBreak + `Render`) and `line_width` (default 120, 0 = unlimited). First consumer: `where_wrap: when_long` (`dmlWhereWhenLong`). _Still TODO: move the remaining DML builders (select lists, CASE, joins, subqueries) from string assembly onto Doc._
 - _Still TODO: LSP range formatting._
 
 ## ✅ Config expansion — DataGrip settings parity