ocaml: phase 6 Float module fleshed out (+6 tests, 598 total)

New Float members:
  zero / one / minus_one
  abs / neg
  add / sub / mul / div     (lift host '+.' '-.' '*.' '/.')
  max / min                 (if-based)
  equal / compare           (Float.compare returns -1 / 0 / 1)
  to_int                    (host floor)
  of_int                    (identity in dynamic runtime)
  of_string                 (delegates to _int_of_string)

Aligns Float with Int's API and lets baselines use Float.add /
Float.compare / etc without lifting the symbols themselves.

  Float.add 3.5 4.5         = 8
  Float.compare 2.5 5.0     = -1
  Float.abs -3.7            = 3.7
  Float.max 3.14 2.71       = 3.14

plans/ocaml-on-sx.md

@@ -407,6 +407,12 @@ _Newest first._
   binary search tree (`type 'a tree = Leaf | Node of 'a * 'a tree *
   'a tree`) with insert + in-order traversal. Tests parametric ADT,
   recursive match, List.append, List.fold_left.
+- 2026-05-09 Phase 6 — Float module fleshed out (+6 tests, 598
+  total). New Float members: zero, one, minus_one, abs, neg, add,
+  sub, mul, div, max, min, equal, compare, to_int, of_int,
+  of_string. Most just lift the host operators (`+.` is already
+  available as a global). Aligns Float with Int module's API and
+  unblocks idiomatic float arithmetic in baselines.
 - 2026-05-09 Phase 5.1 — balance.ml baseline (paren/bracket/brace
   balance using Stack). is_balanced walks a string; on opener push,
   on closer check stack non-empty + top matches expected opener (else