Introduce a shared meld engine and four games built on it, all on
cg-core/EIEIO with console UNICODE rendering.
* cg-rummy.el: the meld engine and Gin Rummy. Set/run validation,
candidate-meld enumeration, a bitmask-DP minimum-deadwood partition,
and a layoff finder, plus the abstract cg-rummy-game base and shared
render helpers. Gin is two-handed with draw/take/discard/knock, gin
and undercut bonuses, opponent layoffs, and play to 100.
* cg-rum500.el: the abstract cg-tablemeld-game (one mode and command
set, dispatching on the subclass) driving Basic Rummy (meld out;
score the cards left in other hands; to 100) and Rummy 500 (score the
cards you lay down, lose those left in hand; ace high and worth 15;
to 500).
* cg-handfoot.el: Hand & Foot, a partnership Canasta cousin. Hand and
foot packets, Twos and Jokers wild, rank books with clean/dirty piles,
go-out bonus, and partnership scoring to 5000. Deliberately
Host-authoritative networked 500: host sits South, joiners take W/N/E,
open seats filled by AI. Per-seat rotated state hides other hands and the
kitty; clients reuse the single-player renderer/commands via :around advice,
so cg-bid.el/cg-bid-ui.el are untouched. Adds cg-bid-host/cg-bid-join, a
start-now lobby with auto-start at four players, and cg-bid-shuffle-partners.
cg-net.el gains cg-net-connect-functions. Verified: clean byte-compile,
checkdoc, 34/34 ERT (incl. 3 new net tests) and a two-process TCP game.
