fix(stdlib): revert CHANGELOG edit and align reduce callback with Itertools

- Revert CHANGELOG.md (AGENTS.md forbids PR edits to it).
- Use System.Func<_,_,_> for reduce's binary callback to match the
  accumulate convention in Itertools and ensure Fable uncurries the
  callable before Python invokes it with two positional arguments.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: dbrattli

CHANGELOG.md

@@ -23,10 +23,6 @@ All notable changes to this project will be documented in this file.
 
 ## Unreleased
 
-### 🚀 Features
-
-* *(stdlib)* Add functools module bindings (`reduce`, `lruCache`, `cache`) with 6 tests
-
 ### 🐞 Bug Fixes
 
 * Fix `math.factorial` binding: changed signature from `float -> float` to `int -> int` to match Python 3.12+ where float arguments raise `TypeError`. Fixes test to use integer literals.

src/stdlib/Functools.fs

@@ -14,13 +14,13 @@ type IExports =
     /// Apply a function of two arguments cumulatively to the items of an iterable,
     /// reducing it to a single value (fold-left without a seed).
     /// See https://docs.python.org/3/library/functools.html#functools.reduce
-    abstract reduce: func: ('T -> 'T -> 'T) * iterable: 'T seq -> 'T
+    abstract reduce: func: System.Func<'T, 'T, 'T> * iterable: 'T seq -> 'T
 
     /// Apply a function of two arguments cumulatively to the items of an iterable,
     /// starting with the initializer as the seed value (fold-left with a seed).
     /// See https://docs.python.org/3/library/functools.html#functools.reduce
     [<Emit("$0.reduce($1, $2, $3)")>]
-    abstract reduce: func: ('State -> 'T -> 'State) * iterable: 'T seq * initializer: 'State -> 'State
+    abstract reduce: func: System.Func<'State, 'T, 'State> * iterable: 'T seq * initializer: 'State -> 'State
 
     // ========================================================================
     // Caching decorators