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.

lib/ocaml/test.sh

@@ -946,6 +946,16 @@ cat > "$TMPFILE" << 'EPOCHS'
 (epoch 2503)
 (eval "(ocaml-run \"match \`Pair (1, 2) with | \`Pair (a, b) -> a + b\")")
 
+;; ── Record patterns ───────────────────────────────────────────
+(epoch 2600)
+(eval "(ocaml-run \"match { x = 1; y = 2 } with | { x = a; y = b } -> a + b\")")
+(epoch 2601)
+(eval "(ocaml-run \"match { name = \\\"Bob\\\"; age = 30 } with | { name = n; age = a } -> a\")")
+(epoch 2602)
+(eval "(ocaml-run \"match { x = 1; y = 2 } with | { x = 1; y = y } -> y | _ -> 0\")")
+(epoch 2603)
+(eval "(ocaml-run \"match { x = 5; y = 2 } with | { x = 1; y = y } -> y | _ -> 0\")")
+
 EPOCHS
 
 OUTPUT=$(timeout 180 "$SX_SERVER" < "$TMPFILE" 2>/dev/null)
@@ -1496,6 +1506,12 @@ check 2501 "polyvar Some 42"              '("Some" 42)'
 check 2502 "polyvar match"                '1'
 check 2503 "polyvar Pair (a,b)"           '3'
 
+# ── Record patterns ────────────────────────────────────────────
+check 2600 "match record bind both"       '3'
+check 2601 "match record name+age"        '30'
+check 2602 "match record literal x=1"     '2'
+check 2603 "match record literal fail"    '0'
+
 TOTAL=$((PASS + FAIL))
 if [ $FAIL -eq 0 ]; then
   echo "ok $PASS/$TOTAL OCaml-on-SX tests passed"