`surfaceConfig.env_vars` are overrides layered on top of Ghostty's
default subprocess environment. Starting the env map from
`ProcessInfo.processInfo.environment` re-introduced variables that
Ghostty intentionally strips (e.g. LANGUAGE, Xcode DYLD vars),
bypassing its env filtering.
Start with an empty map and add `getenv()` fallbacks for PATH, SHELL,
ZDOTDIR, and GHOSTTY_RESOURCES_DIR so critical values are still
resolved without leaking the full app environment.
fd756dccce