Port a mod faithfully

When porting an existing mod, the original is the spec. A port rarely fails for lack of code. It fails by drift:

• values recalled from memory or a wiki;
• mechanics borrowed from a later rewrite of the same mod;
• quiet "improvements";
• renderers that look roughly right;
• checks that the original made on the client and the port forgot.

The method below carried a Thaumcraft 4.2.3.5 port from Minecraft 1.7.10 Forge to 1.20.1 Fabric:

• 859 original classes became about 77,000 lines of port code;
• 323 GameTests cover it, and scripted real-client scenarios check what tests can't reach;
• the work spanned many sessions and two agent accounts.

The field note knowledge/games/minecraft/porting-thaumcraft-4-1-7-10-forge-to-minecraft-1-20-1-fabric.md has its gotchas. Minecraft-specific mappings are in references/minecraft-1-7-10-forge-to-1-20-fabric.md.