ocaml: phase 5 parse ctor arg types in user type-defs (+3 tests, 409 total)

ocaml-hm-parse-type-src recognises primitive type names (int/bool/
string/float/unit), tyvars 'a, and simple parametric T list / T option.
Replaces the previous int-by-default placeholder in
ocaml-hm-register-type-def!.

So 'type tag = TStr of string | TInt of int' correctly registers
TStr : string -> tag and TInt : int -> tag. Pattern-match on tag
gives proper field types in the body. Multi-arg / function types
still fall back to a fresh tv.

lib/ocaml/test.sh

@@ -1004,6 +1004,14 @@ cat > "$TMPFILE" << 'EPOCHS'
 (epoch 3005)
 (eval "(ocaml-run \"String.index_of \\\"hello\\\" \\\"ll\\\"\")")
 
+;; ── HM with parsed ctor arg types ──────────────────────────────
+(epoch 3100)
+(eval "(ocaml-type-of-program \"type shape = Circle of int | Square of int;; let area s = match s with | Circle r -> r * r | Square s -> s * s;; area\")")
+(epoch 3101)
+(eval "(ocaml-type-of-program \"type tag = TStr of string | TInt of int;; TStr \\\"hi\\\"\")")
+(epoch 3102)
+(eval "(ocaml-type-of-program \"type t = A of bool | B of float;; A true\")")
+
 EPOCHS
 
 OUTPUT=$(timeout 180 "$SX_SERVER" < "$TMPFILE" 2>/dev/null)
@@ -1588,6 +1596,11 @@ check 3003 "String.split_on_char"         '("a" "b" "c")'
 check 3004 "String.replace_all"           '"herro"'
 check 3005 "String.index_of"              '2'
 
+# ── HM with parsed ctor arg types ──────────────────────────────
+check 3100 "shape -> Int"                 '"shape -> Int"'
+check 3101 "TStr 'hi' : tag"              '"tag"'
+check 3102 "A true : t"                   '"t"'
+
 TOTAL=$((PASS + FAIL))
 if [ $FAIL -eq 0 ]; then
   echo "ok $PASS/$TOTAL OCaml-on-SX tests passed"