ocaml: phase 1 tokenizer (+58 tests) — consumes lib/guest/lex.sx

Idents, ctors, 51 keywords, numbers (int/float/hex/exp/underscored),
strings + chars with escapes, type variables, 26 op/punct tokens, and
nested (* ... *) block comments. Tests via epoch protocol against
sx_server.exe.

plans/ocaml-on-sx.md

@@ -116,14 +116,15 @@ SX CEK evaluator (both JS and OCaml hosts)
 
 ### Phase 1 — Tokenizer + parser
 
-- [ ] **Tokenizer:** keywords (`let`, `rec`, `in`, `fun`, `function`, `match`, `with`,
+- [x] **Tokenizer:** keywords (`let`, `rec`, `in`, `fun`, `function`, `match`, `with`,
       `type`, `of`, `module`, `struct`, `end`, `functor`, `sig`, `open`, `include`,
       `if`, `then`, `else`, `begin`, `try`, `exception`, `raise`, `mutable`,
       `for`, `while`, `do`, `done`, `and`, `as`, `when`), operators (`->`, `|>`,
       `<|`, `@@`, `@`, `:=`, `!`, `::`, `**`, `:`, `;`, `;;`), identifiers (lower,
-      upper/ctor, labels `~label:`, optional `?label:`), char literals `'c'`,
-      string literals (escaped + heredoc `{|...|}`), int/float literals,
-      line comments `(*` nested block comments `*)`.
+      upper/ctor), char literals `'c'`, string literals (escaped),
+      int/float literals (incl. hex, exponent, underscores), nested block
+      comments `(* ... *)`. _(labels `~label:` / `?label:` and heredoc `{|...|}`
+      deferred — surface tokens already work via `~`/`?` punct + `{`/`|` punct.)_
 - [ ] **Parser:** top-level `let`/`let rec`/`type`/`module`/`exception`/`open`/`include`
       declarations; expressions: literals, identifiers, constructor application,
       lambda, application (left-assoc), binary ops with precedence table,
@@ -308,7 +309,12 @@ the "mother tongue" closure: OCaml → SX → OCaml. This means:
 
 _Newest first._
 
-_(awaiting phase 1)_
+- 2026-05-07 Phase 1 — `lib/ocaml/tokenizer.sx` consuming `lib/guest/lex.sx`
+  via `prefix-rename`. Covers idents, ctors, 51 keywords, numbers (int / float
+  / hex / exponent / underscored), strings (with escapes), chars (with escapes),
+  type variables (`'a`), nested block comments, and 26 operator/punct tokens
+  (incl. `->` `|>` `<-` `:=` `::` `;;` `@@` `<>` `&&` `||` `**` etc.). 58/58
+  tokenizer tests pass via `lib/ocaml/test.sh` driving `sx_server.exe`.
 
 ## Blockers