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cg-core: make cg-shuffle optionally seeded and reproducible

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cg-shuffle gains an optional SEED and a `cg-shuffle-seed' dynamic var.
With a seed the order is deterministic and identical on every platform,
so a deal can be replayed, shared between players, or pinned in a test;
the index comes from secure-hash (spec-defined output everywhere, 7 hex
digits stay a fixnum even on 32-bit Emacs), so no bignum/overflow
behaviour can vary it.  With no seed the shuffle is the byte-for-byte
old system-random path -- normal play is unchanged.

Test cgt-shuffle-seeded pins determinism, permutation, override and a
cross-platform golden prefix; fails on the prior one-arg cg-shuffle.
Suite 159/159.
This commit is contained in:
Corwin Brust 2026-08-03 22:18:02 -05:00
parent 1a59003b13
commit 6379127e17
8 changed files with 180 additions and 15 deletions
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card-games.el
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;;; card-games.el --- Play card games in Emacs (console + SVG) -*- lexical-binding: t; -*-
;;; card-games.el --- Play card games (console + SVG) -*- lexical-binding: t; -*-
;; Copyright (C) 2026 Corwin Brust