ocaml: phase 6 Float module: sqrt/sin/cos/pow/floor/ceil/round/pi (+6 tests, 378 total)

Wraps host SX math primitives via _float_* builtins. Float.pi is a
Float literal in the OCaml-side module.

plans/ocaml-on-sx.md

@@ -266,7 +266,8 @@ SX CEK evaluator (both JS and OCaml hosts)
       _(Pending: escaped.)_
 - [~] `Int`: `to_string`, `of_string`, `abs`, `max`, `min`.
       _(Pending: arithmetic helpers, min_int/max_int.)_
-- [~] `Float`: `to_string`. _(Pending: of_string, arithmetic helpers.)_
+- [~] `Float`: `to_string`, `sqrt`, `sin`, `cos`, `pow`, `floor`,
+      `ceil`, `round`, `pi`. _(Pending: of_string.)_
 - [~] `Printf`: stub `sprintf`/`printf`. _(Real format-string
       interpretation pending.)_
 - [ ] `String`: `length`, `get`, `sub`, `concat`, `split_on_char`, `trim`,
@@ -373,6 +374,9 @@ the "mother tongue" closure: OCaml → SX → OCaml. This means:
 
 _Newest first._
 
+- 2026-05-08 Phase 6 — Float module: sqrt/sin/cos/pow/floor/ceil/round
+  + pi constant (+6 tests, 378 total). Wraps host SX math primitives
+  via `_float_*` builtins.
 - 2026-05-08 Phase 1+5+6 — Float arithmetic (`+.` `-.` `*.` `/.`)
   (+5 tests, 372 total). Tokenizer recognises the dotted operators.
   Parser table places them at int's level (7 / 8). Eval routes them