ocaml: phase 1 unit/wildcard params + 180s timeout (+5 tests, 283 total)

Parser: try-consume-param! handles ident, wildcard _ (fresh __wild_N
name), unit () (fresh __unit_N), typed (x : T) (skips signature).
parse-fun and parse-let (inline) reuse the helper; top-level
parse-decl-let inlines a similar test.

test.sh timeout bumped from 60s to 180s — the growing suite was hitting
the cap and reporting spurious failures.

plans/ocaml-on-sx.md

@@ -343,6 +343,12 @@ the "mother tongue" closure: OCaml → SX → OCaml. This means:
 
 _Newest first._
 
+- 2026-05-08 Phase 1 — unit `()` and wildcard `_` parameters in `let f ()
+  = …` / `fun _ -> …` / `let f _ = …`. Parser helper `try-consume-param!`
+  now handles ident, wildcard `_` (renamed to `__wild_N`), unit `()`
+  (renamed to `__unit_N`), and typed `(x : T)` (signature skipped).
+  Same for top-level `parse-decl-let`. test.sh timeout extended from
+  60s to 180s for the growing suite. 283/283 (+5).
 - 2026-05-08 Phase 6 — extended stdlib slice (+13 tests, 278 total).
   Host primitives exposed via `_string_*`, `_char_*`, `_int_*`,
   `_string_of_*` underscore-prefixed builtins so the OCaml-side