Add focused coverage for the new GLib command stream helper.
These tests verify that complete lines are emitted as they arrive and that EOF flushes a final unterminated line without duplicating a newline-terminated one.
That behavior is the contract the custom module will rely on when its continuous command handling moves onto this helper.
Signed-off-by: Austin Horstman <khaneliman12@gmail.com>
Austin Horstman