Phosphor::Logger
Configures Crystal's Log module to write file-only, structured
output — never STDOUT/STDERR, since a TUI owns the terminal and any
stray write there corrupts the display.
See DESIGN.md § "Logging: file-only, structured, Crystal's Log stdlib".
Class methods
${XDG_STATE_HOME:-$HOME/.local/state}/phosphor/<app_name>.log.
setup(app_name : String, log_path : String | Nil = nil, log_max_size : Int32 = (10 * 1024) * 1024, log_keep : Int32 = 5) : Void
Points every Log source ("*") at a FileBackend writing to
log_path (or the default XDG path derived from app_name),
rotating at log_max_size bytes and keeping log_keep old files.
Called once, early in App#run, before any component logs.