- ConsoleInputPump gains an optional ILogger so the reader-fault and
command-dispatch catch blocks log warnings/errors again, matching the
behavior the old ConsoleInputHandler had before the pump refactor.
- Remove ConsoleInputPump.Stop() — dead code, nothing calls it; the reader
thread already terminates on EOF/Core.Closing/finally cleanup.
- GetInputCommand no longer clears the help-description cache on every
lookup; RegisterCommand/UnregisterInputCommand still invalidate it
correctly on the paths that actually change the command set.
ConsoleInputHandler.Initialize() now checks Core.Headless and skips
starting the input thread entirely when stdin isn't a TTY, logging
instead. When not headless, it delegates the read loop to
ConsoleInputPump (Task 2) rather than running its own async void
loop with a two-AutoResetEvent handshake.
ReadLine() throws HeadlessConsoleInputException when headless, falls
back to a direct Console.ReadLine() during early startup or after the
pump loop has ended, and otherwise blocks on the pump.
