refactor: extract ports/drivers/bins layers — clean dependency inversion

Separate abstractions from implementations following DIP:

  servers/              drivers/
      │                     │
      ▼                     ▼
    ports/  (trait-only crates, zero deps)

New crates:

ports/ (abstractions):
  - port-framebuffer: Framebuffer trait
  - port-block-device: BlockDevice trait + SectorId
  - port-input-device: InputDevice trait + InputEvent types

drivers/ (implementations depend on ports/):
  - driver-framebuffer-virtio: VirtIO GPU framebuffer
  - driver-framebuffer-mock: test double
  - driver-block-virtio: VirtIO block device

bins/ (composition roots wire server + driver):
  - display-qemu: DisplayServer<VirtioFramebuffer>
  - storage-qemu: storage server with VirtIO block

Servers no longer own their hardware traits or driver code.
Neither server nor driver depends on the other — both point
inward to the port abstraction.

crates/servers/input-server/src/adapters/mock.rs

@@ -1,5 +1,4 @@
-use crate::input_device::InputDevice;
-use crate::protocol::InputEvent;
+use crate::input_device::{InputDevice, InputEvent};
 
 pub struct MockInputDevice {
     events: [Option<InputEvent>; 16],

crates/servers/input-server/src/adapters/qemu_uart.rs

@@ -1,5 +1,4 @@
-use crate::input_device::InputDevice;
-use crate::protocol::{InputEvent, Key};
+use crate::input_device::{InputDevice, InputEvent, Key};
 
 const UART_BASE: usize = 0x10000000;
 const UART_LSR: usize = 5;

crates/servers/input-server/src/input_device.rs

@@ -1,6 +1 @@
-use crate::protocol::InputEvent;
-
-pub trait InputDevice {
-    fn poll(&mut self) -> Option<InputEvent>;
-    fn has_event(&self) -> bool;
-}
+pub use port_input_device::{InputDevice, InputEvent, Key, GamepadButton, Axis};

crates/servers/input-server/src/protocol.rs

@@ -1,55 +1,5 @@
 use server_framework::{Decode, Encode};
-
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub enum Key {
-    Up,
-    Down,
-    Left,
-    Right,
-    Enter,
-    Escape,
-    Space,
-    Backspace,
-    Tab,
-    Char(u8),
-}
-
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub enum GamepadButton {
-    South,
-    East,
-    North,
-    West,
-    DpadUp,
-    DpadDown,
-    DpadLeft,
-    DpadRight,
-    Start,
-    Select,
-}
-
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub enum Axis {
-    LeftX,
-    LeftY,
-    RightX,
-    RightY,
-}
-
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub enum InputEvent {
-    KeyDown(Key),
-    KeyUp(Key),
-
-    PointerDown { id: u8, x: u16, y: u16 },
-    PointerMove { id: u8, x: u16, y: u16 },
-    PointerUp { id: u8, x: u16, y: u16 },
-
-    Scroll { dx: i16, dy: i16 },
-
-    GamepadButton { button: GamepadButton, pressed: bool },
-    GamepadAxis { axis: Axis, value: i16 },
-}
+pub use port_input_device::{Key, GamepadButton, Axis, InputEvent};
 
 #[derive(Debug, PartialEq)]
 pub enum InputRequest {
@@ -82,7 +32,6 @@ impl Decode for InputRequest {
     }
 }
 
-// Event type tags for encoding
 const EV_KEY_DOWN: usize = 1;
 const EV_KEY_UP: usize = 2;
 const EV_PTR_DOWN: usize = 3;