ocaml: phase 1+3 record patterns { f = pat } (+4 tests, 386 total)

Parser: { f1 = pat; f2 = pat; ... } in pattern position emits
(:precord (FIELDNAME PAT)...). Mixed with the existing { in
expression position via the at-pattern-atom? whitelist.

Eval: :precord matches against a dict; required fields must be present
and each pat must match the field's value. Can mix literal+var:
'match { x = 1; y = y } with | { x = 1; y = y } -> y' matches only
when x is 1.

plans/ocaml-on-sx.md

@@ -134,13 +134,12 @@ SX CEK evaluator (both JS and OCaml hosts)
       `type`/`module`/`exception`/`open`/`include` decls, `try`/`with`,
       `function`, record literals/updates, field access, `and` mutually-recursive
       bindings.)_
-- [~] **Patterns:** constructor (nullary + with args, incl. flattened tuple
-      args `Pair (a, b)` → `(:pcon "Pair" PA PB)`), literal (int/string/char/
-      bool/unit), variable, wildcard `_`, tuple, list cons `::`, list
-      literal, `as` binding (`pat as name`). Match clauses support `when`
-      guard via `(:case-when PAT GUARD BODY)`. _(Pending: record patterns,
-      or-pattern `P1 | P2` — ambiguous with clause separator without
-      lookahead.)_
+- [x] **Patterns:** constructor (nullary + with args, incl. flattened tuple
+      args), literal (int/string/char/bool/unit), variable, wildcard `_`,
+      tuple, list cons `::`, list literal, record `{ f = pat; … }`,
+      `as` binding. Match clauses support `when` guard via
+      `(:case-when PAT GUARD BODY)`. _(Pending: or-pattern `P1 | P2` —
+      ambiguous with clause separator without lookahead.)_
 - [ ] OCaml is **not** indentation-sensitive — no layout algorithm needed.
 - [ ] Tests in `lib/ocaml/tests/parse.sx` — 50+ round-trip parse tests.
 
@@ -377,6 +376,12 @@ the "mother tongue" closure: OCaml → SX → OCaml. This means:
 
 _Newest first._
 
+- 2026-05-08 Phase 1+3 — record patterns `{ f = pat; … }` (+4 tests,
+  386 total). Parser adds `(:precord (FIELD PAT) …)` alongside
+  the existing record-literal `{` handling. Eval matches against
+  dicts: required fields must be present and each pat must match the
+  value. Can mix with literals: `{ x = 1; y = y }` matches only when
+  x is 1.
 - 2026-05-08 Phase 5.1 — expr_eval.ml baseline (9/9 pass). A tiny
   arithmetic-expression evaluator using ADT (`type expr = Lit | Add |
   Mul | Neg`) + recursive eval + pattern match — exercises the full