SMBC gets its project skeleton

Started SMBC, a C port of doppelganger's Super Mario Bros. disassembly. The disassembly stays unmodified as the source of truth; the C is a faithful translation, with every ported routine citing the assembly label it came from.

Skeleton

The repo follows the standard conventions: AGPL-3.0-only, root and src AGENTS.md, scoped/atomic paths (src/<scope>/<atom>.c), C23 with warnings-as-errors, and host tests mirroring the source scopes.

Seeded so far: an NES hardware model (hw/ppu with the $2005/$2006 write-pair latch, hw/apu register capture, hw/joypad strobe-and-shift), a flat 2KB RAM map with named offsets from the disassembly's defines, and a frame loop derived from the NMI joypad poll. make runs 60 headless frames; make test is green.