feat(format): implement subquery and CASE expression formatting

* Add support for formatting subqueries with configurable placement and spacing.
* Implement CASE expression formatting with options for wrapping and collapsing.
* Introduce tests for subquery and CASE expression scenarios to ensure correctness.

docs/todo.md

@@ -209,15 +209,31 @@ to route ident tokens through `AliasCase` (after AS) or `BuiltinCase` (before `(
 - `space_after_comma_in_calls` applied in `dmlInline`.
 - `binary_op_align` registered in config (enforcement in WHERE/expression context deferred).
 
-### ⬜ Formatter — subquery formatting
+### ✅ Formatter — subquery formatting
 
-`subquery_opening/content/closing/space_before_paren` fields are wired in config.
-Enforcement in `dml.go` is not yet implemented — subqueries use current CTE formatting
-as a proxy (new_line for content, inline for single-arg subexpressions).
+`pkg/format/dml.go`: `dmlIsSubqueryOpen` detects a `(` immediately followed by `SELECT`/
+`WITH` (derived tables, scalar subqueries, `IN`/`EXISTS`/`ARRAY(...)` subqueries — a plain
+value tuple like `IN (1, 2, 3)` is left alone). `dmlInline` splices these in via
+`dmlWrapSubquery`, which recursively formats the inner tokens with `formatDML` and wraps
+them per `subquery_content`/`subquery_closing`; `dmlWriteSubquerySep` handles
+`subquery_opening` (same_line/new_line) and additively applies `subquery_space_before_paren`
+(only adds a space where one wouldn't already be there — never removes the space `IN`/
+`EXISTS`/`AS` already get). `formatCTEDef` now calls the same `dmlWrapSubquery` helper
+instead of a hardcoded new_line-only layout, so CTE bodies honor the config too (the
+`AS (` space itself stays unconditional — that's fixed CTE syntax, not the subquery-space
+setting). Nested subqueries-in-CASE and CASE-in-subqueries recurse correctly. Not
+column/Doc-IR-aligned (documented "fixed-layout, not Wadler" limitation) — wrapped content
+is indented one level relative to its own local frame, which composes correctly under
+JOIN/WHERE/SELECT-list embedding but isn't perfectly column-aligned for deeply nested cases.
+Tests: `TestDMLSubquery*`, `TestDMLCTEUsesSubqueryConfig` in `pkg/format/dml_test.go`.
 
-### ⬜ Formatter — INSERT VALUES collapse
+### ✅ Formatter — INSERT VALUES collapse
 
-`insert_collapse_values` field is wired in config. Enforcement in `dml.go` not yet implemented.
+`dmlValuesClause` (`pkg/format/dml.go`): when `insert_collapse_values` is `true` (default)
+multi-row `VALUES` stays packed on one line (matches prior behavior); when `false`, each row
+gets its own line via the shared `dmlCommaList` helper (same leading/trailing-comma layout
+as SELECT/SET lists). Single-row VALUES is unaffected either way.
+Tests: `TestDMLInsertValues*`.
 
 ### ✅ Formatter — routine param alignment (`pkg/format/format.go`)
 
@@ -238,9 +254,27 @@ as a proxy (new_line for content, inline for single-arg subexpressions).
   collapses them to one line.
 - CRLF normalization in trivia emission (comment text, body trivia before DECLARE).
 
-### ⬜ Formatter — expression settings (case_when_wrap, case_end, case_collapse, record_space_before_paren)
+### ✅ Formatter — expression settings (case_when_wrap, case_end, case_collapse, record_space_before_paren)
 
-Config fields wired. Expression-level CASE/ROW formatting not yet implemented.
+`pkg/format/dml.go`: `dmlInline` detects `CASE` tokens (`dmlIsCaseStart`/`dmlMatchCaseEnd`,
+tracking nested-CASE depth so an inner `CASE…END`'s own `WHEN`/`THEN`/`ELSE` don't get
+mistaken for the outer one's boundaries) and splices in `dmlFormatCase`. `dmlSplitCase`
+breaks the body into operand/WHEN/THEN/ELSE segments (each rendered via a recursive
+`dmlInline` call, so subqueries and nested CASEs inside a branch format correctly too).
+Both the simple (`CASE x WHEN ...`) and searched (`CASE WHEN ...`) forms are supported.
+- `case_when_wrap` (default `false`): `false` keeps everything on one line (unchanged
+  default behavior); `true` puts each `WHEN … THEN …` and `ELSE` on its own line, indented
+  one level.
+- `case_end` (default `new_line`): placement of the closing `END` when wrapped —
+  `new_line` on its own line, `same_line` glued to the last WHEN/ELSE line.
+- `case_collapse` (default `false`): when `true` *and* the fully-inlined rendering is
+  ≤ `caseCollapseWidth` (60 chars), keeps the wrapped CASE on one line anyway, overriding
+  `case_when_wrap`; longer CASEs still wrap. (No Doc-IR/line-width awareness exists yet, so
+  this is a fixed length threshold rather than a true "does it fit the line" check.)
+- `record_space_before_paren` (default `false`): scoped to the `ROW` keyword specifically
+  (`ROW(1, 2)` vs `ROW (1, 2)`) — bare `(a, b)` record literals are indistinguishable from
+  grouping parens at the token level, so this setting only fires on an explicit `ROW(`.
+Tests: `TestDMLCase*`, `TestDMLRecordSpaceBeforeParen`.
 
 ### ⬜ DataGrip XML import/export (optional, V4+)