`Bags/Grid.lua` and `Merchant/Grid.lua` are one grid.

The same functions in the same order: Subject, Enter, Leave, Build, Paint, Place, Trim, then Attach, Paint, the pool, Headers and Describe.

Weaker than it was. The merchant's unit is a card in columns worked out from the window's width and the bag's is a bare square in a column count you set, so what is shared is the pile walk and the pool. Ranked last of the seven, and the way to find out is to write the shared grid and see what will not fit through it.

Items 53 to 59 came out of an ask on 2026-09-04: write down what every class and build needs before any of them is written. Nine classes, twenty-seven builds, four class files on disk. Five rules settle most of it.

• A class file is facts and one file, src/Class/Class.lua:27. That holds for eleven of the twelve fields; standing is the exception and item 53 says what it costs.
• The fields are listed at src/Class/Warrior.lua:11. forms, charge, reactive, requires, swing, upkeep, suggested and standing go at the top; cooldowns, rotation, debuffs and loadout go inside a spec, which writes only what it disagrees with. Caps are eight, six and four, asserted in Cooldowns.All and Upkeep.Fixed, and they fire at PLAYER_LOGIN as a Lua error in somebody's game.
• No item carries a spell id. Bake them at implementation from Wowhead's TBC Classic database, rank 1, and read each back by name; drop what this client cannot resolve rather than guessing. An ability with no cooldown comes off the rotation line.
• No item writes a loadout. src/Class/Shaman.lua:37 and src/Class/Priest.lua:17 refuse a plan for a build nobody here has played, which covers twenty-four of the twenty-seven.
• No item writes a signature. src/Class/Spec.lua:54 wants a one-rank talent at the foot of a tree; each item names the tree instead, and the signature is confirmed a rank at a time or left out.