[abalakh]

Every user-facing string was English. Cheevos now reads Spruce's UI language from PyUI when a session starts and applies its translation from src/cheevos/res/lang/.json, named as PyUI names its own language files. Translations ship with Cheevos rather than in PyUI's lang/ files, so a release's string names and {fields} always match its translations. None ships yet, so English is unchanged.

• Add ui/language.py: loads a translation over the English values in strings.py. A missing string stays English, and so does a value that wouldn't format like the English one (an unknown or missing field, another format spec, a stray brace, the wrong shape). Each is logged.
• Add ui/plurals.py with CLDR's rules for the languages PyUI has. Strings that count by {count} are now Plural values, formatted with format.count(). POINT, AWARDS_EVENT, MORE_CONSOLE and EVENT_POINT became the "one" forms of their plurals, and {points}, {days} and {minutes} became {count}.
• Make dates and numbers translatable: MONTHS, DATE, DATETIME, the separators, PERCENT, SIZE and SIZE_UNITS replace strftime's %b and hard-coded formats.
• Read strings when the text is shown. The relative-time steps, the keyboard hints and the sync failure messages were read at import and would have stayed English. check_conventions.py now rejects that (CV007).
• Break text without spaces (Chinese, Japanese) where the line ends. wrap() moves to ui/pyui/text.py. The achievement card's detail lines wrap instead of running off the screen.
• Desktop: --lang, or UI_LANGUAGE= for make run and make screens, shows the app and PyUI's own text in that language, with screenshots in build/screens//. UI_LANGUAGE=Pseudo is a generated language (accented, longer, bracketed) that shows text that can't be translated or gets cut. make languages checks the translations and writes the English template to build/lang/English.json.
• Docs: "Translating" in CONTRIBUTING.md, "Languages" in TESTING.md and .agents/product.md, code.md, pyui.md, AGENTS.md, and a Language section on the wiki's Themes and devices page. res/lang/README.md ships in the package, so someone who finds the folder in Spruce's App/Cheevos knows to send translations here.

English screens are pixel-identical to before. Counts now take their singular ("1 game", not "1 games"), and Home's game count gets a thousands separator.