Expand roadmap with detailed implementation plans for the next three
features: MBF binary file compatibility (token-stream conversion at
load/save boundary), hardware I/O simulator (portio.c with PIT/speaker/
CGA/joystick port emulation), and DRAW command fixes (M parsing bug,
scale semantics, A rotation, TA/variable substitution). Remove hardware
I/O from known limitations (moving to planned). Fix stale test counts
(64 -> 66) and version string (0.11.0 -> 0.13.0) across docs.
c488cb526d