The picked fix inlined the platform ternary inside terminalShellEnv(), which
reads process.platform and can only be exercised by booting Electron. Lift it
into a pure terminalLcCtype(env, platform) that takes the platform as data
(root AGENTS.md: never fake the host OS) and pin the contract with one vitest:
Linux reuses LANG, falls back to C.UTF-8, respects an explicit LC_CTYPE; macOS
keeps the bare "UTF-8" it accepts. Red on origin/main (helper absent), green here.
5b0103ffdc