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

plans/ocaml-on-sx.md

@@ -137,9 +137,9 @@ SX CEK evaluator (both JS and OCaml hosts)
 - [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.)_
+      `as` binding, or-pattern `(P1 | P2 | …)` (parens-only — top-level
+      `|` is the clause separator). Match clauses support `when` guard
+      via `(:case-when PAT GUARD BODY)`.
 - [ ] OCaml is **not** indentation-sensitive — no layout algorithm needed.
 - [ ] Tests in `lib/ocaml/tests/parse.sx` — 50+ round-trip parse tests.
 
@@ -377,6 +377,11 @@ the "mother tongue" closure: OCaml → SX → OCaml. This means:
 
 _Newest first._
 
+- 2026-05-08 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 the first match. Top-level `|` remains the clause separator (no
+  lookahead needed). Examples: `(1 | 2 | 3) -> ...`, `(Red | Green) -> 1`.
 - 2026-05-08 Phase 4 — `module type S = sig … end` parser (+3 tests,
   389 total). Signatures are parsed-and-discarded — sig..end balanced
   skipping. AST: `(:module-type-def NAME)`. Runtime no-op (signatures