ocaml: phase 4 functors + module aliases (+5 tests, 225 total)

Parser: module F (M) (N) ... = struct DECLS end -> (:functor-def NAME
PARAMS DECLS). module N = expr (non-struct) -> (:module-alias NAME
BODY-SRC). Functor params accept (P) or (P : Sig) — signatures
parsed-and-skipped via skip-optional-sig.

Eval: ocaml-make-functor builds curried host-SX closures from module
dicts to a module dict. ocaml-resolve-module-path extended for :app so
F(A), F(A)(B), and Outer.Inner all resolve to dicts.

Phase 4 LOC ~290 cumulative (still well under 2000).

plans/ocaml-on-sx.md

@@ -181,11 +181,13 @@ SX CEK evaluator (both JS and OCaml hosts)
 
 - [x] `module M = struct let x = 1 let f y = x + y end` → SX dict
       `{"x" 1 "f" <fn>}`.
-- [ ] `module type S = sig val x : int val f : int -> int end` → interface record
-      (runtime stub; typed checking in Phase 5).
-- [ ] `module M : S = struct ... end` — coercive sealing (runtime: pass-through).
-- [ ] `functor (M : S) -> struct ... end` → SX `(fn (M) ...)`.
-- [ ] `module F = Functor(Base)` — functor application.
+- [~] `module type S = sig val x : int val f : int -> int end` — signature
+      annotations are parsed-and-skipped (`skip-optional-sig`); typed
+      checking deferred to Phase 5.
+- [x] `module M : S = struct ... end` — coercive sealing (signature ignored).
+- [x] `functor (M : S) -> struct ... end` via shorthand `module F (M) = …`.
+- [x] `module F = Functor(Base)` — functor application; multi-param via
+      `module P = F(A)(B)`.
 - [x] `open M` — merge M's dict into current env (via
       `ocaml-env-merge-dict`). Module path `M.Sub` resolves via
       `ocaml-resolve-module-path`.
@@ -325,6 +327,16 @@ the "mother tongue" closure: OCaml → SX → OCaml. This means:
 
 _Newest first._
 
+- 2026-05-08 Phase 4 — functors + module aliases (+5 tests, 225 total).
+  Parser: `module F (M) = struct DECLS end` → `(:functor-def NAME PARAMS
+  DECLS)`. `module N = expr` (where expr isn't `struct`) → `(:module-alias
+  NAME BODY-SRC)`. Functor params accept `(P)` or `(P : Sig)` (signatures
+  parsed-and-skipped). Eval: `ocaml-make-functor` builds a curried
+  host-SX closure that takes module dicts and returns a module dict;
+  `ocaml-resolve-module-path` extended for `:app` so `F(A)`, `F(A)(B)`,
+  `Outer.Inner` all resolve to dicts. Tested: 1-arg functor, 2-arg
+  curried `Pair(One)(Two)`, module alias, submodule alias, identity
+  functor with include. Phase 4 LOC ~290 (still well under 2000).
 - 2026-05-08 Phase 4 — `open M` / `include M` (+5 tests, 220 total).
   Parser: top-level `open Path` / `include Path` decls; path is `Ctor (.
   Ctor)*`. Eval resolves the path via `ocaml-resolve-module-path` (the