PERF.55 Apps: 84 to 95 % of the language keys shipped on an app page are never read; split the catalog by namespace (extends PERF.2)

Instrumented t() on the current releases: CadCraft ships 8,818 keys / 529 KB in #cc-lang, 442 are read by the end of idle and 1,024 after a first command; 70 namespaces (198 KB) are never touched in the first minute (frame 32 KB, m3d 29 KB …); BimCraft 117 namespaces / 300 KB untouched; PartCraft's script namespace 1,140 keys / 73 KB with 13 read; the shell's 1,515 keys / 82 KB with about 300 read in every app. Parsing is cheap (5 to 11 ms); the bytes are the cost, 400 to 500 KB of every page view. Change: split the catalog by namespace at build time (tools/lang), inline shell plus the entry's namespaces, load a namespace on the first t() miss or together with the module that owns it (the dynamic-import row gives the boundary); Lang::merged() key prefix is the split key.