ocaml: phase 1+3 or-patterns (P1 | P2 | ...) parens-only (+5 tests, 394 total)

Parser: when | follows a pattern inside parens, build (:por ALT1 ALT2
...). Eval: try alternatives, succeed on first match. Top-level |
remains the clause separator — parens-only avoids ambiguity without
lookahead.

Examples now work:
  match n with | (1 | 2 | 3) -> 100 | _ -> 0
  match c with | (Red | Green) -> 1 | Blue -> 2

lib/ocaml/test.sh

@@ -964,6 +964,18 @@ cat > "$TMPFILE" << 'EPOCHS'
 (epoch 2702)
 (eval "(ocaml-parse-program \"module type EMPTY = sig end\")")
 
+;; ── or-patterns (parens-only) ─────────────────────────────────
+(epoch 2800)
+(eval "(ocaml-run \"match 1 with | (1 | 2 | 3) -> 100 | _ -> 0\")")
+(epoch 2801)
+(eval "(ocaml-run \"match 2 with | (1 | 2 | 3) -> 100 | _ -> 0\")")
+(epoch 2802)
+(eval "(ocaml-run \"match 5 with | (1 | 2 | 3) -> 100 | _ -> 0\")")
+(epoch 2803)
+(eval "(ocaml-run \"match Red with | (Red | Green) -> 1 | Blue -> 2\")")
+(epoch 2804)
+(eval "(ocaml-run \"match Blue with | (Red | Green) -> 1 | Blue -> 2\")")
+
 EPOCHS
 
 OUTPUT=$(timeout 180 "$SX_SERVER" < "$TMPFILE" 2>/dev/null)
@@ -1525,6 +1537,13 @@ check 2700 "module type S parses"         '("module-type-def" "S")'
 check 2701 "module type then module"      '42'
 check 2702 "module type EMPTY"            '("module-type-def" "EMPTY")'
 
+# ── or-patterns (parens-only) ──────────────────────────────────
+check 2800 "(1|2|3) match 1"              '100'
+check 2801 "(1|2|3) match 2"              '100'
+check 2802 "(1|2|3) match 5"              '0'
+check 2803 "(Red|Green) Red"              '1'
+check 2804 "(Red|Green) Blue"             '2'
+
 TOTAL=$((PASS + FAIL))
 if [ $FAIL -eq 0 ]; then
   echo "ok $PASS/$TOTAL OCaml-on-SX tests passed"