feat: wire display + input servers to snake, fix QEMU 11.x GPU bug

VirtIO GPU: QEMU 11.x has RESOURCE_ATTACH_BACKING (0x0104) and
RESOURCE_FLUSH (0x0106) command types swapped in its legacy MMIO
VirtIO GPU implementation. Workaround: send swapped type values.
Confirmed via QEMU monitor (xp shows correct bytes in memory)
and QEMU trace events (device dispatches to wrong handler).

Display pipeline now works end-to-end:
  adapter → GPU init → create_2d → attach_backing → set_scanout
  display-server → clear(blue) → flush → transfer + resource_flush
  snake → draw commands via IPC → display renders → flush to GPU

Input server:
  - New driver-input-uart crate (reads UART at mapped VA 0x20000)
  - New bins/input-qemu composition root
  - Adapter loads input-server, maps UART MMIO into its address space
  - Init delegates both display_ep (slot 0) and input_ep (slot 1) to snake
  - WASD keys → UART → input-server → IPC → snake direction change

Snake game runs with display and input, exits on wall collision.

Cargo.toml

@@ -48,7 +48,9 @@ members = [
     "crates/drivers/framebuffer/mock",
     "crates/drivers/block/virtio",
     "crates/bins/display-qemu",
+    "crates/bins/input-qemu",
     "crates/bins/storage-qemu",
+    "crates/drivers/input/uart",
     "crates/hw-virtio",
 ]
 resolver = "2"
@@ -105,6 +107,7 @@ port-input-device = { path = "crates/ports/input-device" }
 driver-framebuffer-virtio = { path = "crates/drivers/framebuffer/virtio" }
 driver-framebuffer-mock = { path = "crates/drivers/framebuffer/mock" }
 driver-block-virtio = { path = "crates/drivers/block/virtio" }
+driver-input-uart = { path = "crates/drivers/input/uart" }
 
 # apps
 snake = { path = "crates/apps/snake" }