refactor: apply newtypes throughout userspace API and display types

Every syscall stub now uses proper types from types/ — CapSlot,
EntryPoint, StackPointer, VirtualAddress, PageCount, ProcessId,
PermissionSet, Ticks. The compiler prevents swapping entry/stack,
passing a ProcessId where a CapSlot is expected, or using an
address as a page count.

New display types in types/display.rs:
  - Color(u32) with rgb() constructor
  - ScreenCoord(u16) for x/y positions
  - Dimension(u16) for width/height

Updated throughout:
  - userspace/syscall.rs: all params typed, returns Option instead
    of sentinel usize::MAX
  - server-framework: endpoint param is CapSlot
  - port-framebuffer: trait uses Color, ScreenCoord, Dimension
  - hw-virtio: DmaAddrs uses PhysicalAddress/VirtualAddress,
    GPU commands use Dimension
  - All servers, drivers, bins, apps updated for new signatures
  - permission-manager: process field uses ProcessId
  - PermissionSet: added bits() accessor

89 tests pass, full QEMU boot verified.

crates/servers/display-server/src/tests/protocol.rs

@@ -1,14 +1,15 @@
 use crate::protocol::{DisplayRequest, DisplayResponse};
 use server_framework::{Decode, Encode};
+use types::display::{Color, Dimension, ScreenCoord};
 
 #[test]
 fn draw_rect_roundtrip() {
     let req = DisplayRequest::DrawRect {
-        x: 10,
-        y: 20,
-        w: 100,
-        h: 50,
-        color: 0xFF0000,
+        x: ScreenCoord::new(10),
+        y: ScreenCoord::new(20),
+        w: Dimension::new(100),
+        h: Dimension::new(50),
+        color: Color::from_raw(0xFF0000),
     };
     let words = req.encode();
     let decoded = DisplayRequest::decode(words).unwrap();
@@ -17,7 +18,7 @@ fn draw_rect_roundtrip() {
 
 #[test]
 fn clear_roundtrip() {
-    let req = DisplayRequest::Clear { color: 0x00FF00 };
+    let req = DisplayRequest::Clear { color: Color::from_raw(0x00FF00) };
     let words = req.encode();
     let decoded = DisplayRequest::decode(words).unwrap();
     assert_eq!(decoded, req);
@@ -40,8 +41,8 @@ fn get_dimensions_roundtrip() {
 #[test]
 fn dimensions_response_roundtrip() {
     let resp = DisplayResponse::Dimensions {
-        width: 320,
-        height: 240,
+        width: Dimension::new(320),
+        height: Dimension::new(240),
     };
     let words = resp.encode();
     let decoded = DisplayResponse::decode(words).unwrap();

crates/servers/display-server/src/tests/server.rs

@@ -2,20 +2,21 @@ use driver_framebuffer_mock::MockFramebuffer;
 use crate::protocol::{DisplayRequest, DisplayResponse};
 use crate::server::DisplayServer;
 use server_framework::Server;
+use types::display::{Color, Dimension, ScreenCoord};
 
 fn test_server() -> DisplayServer<MockFramebuffer> {
-    DisplayServer::new(MockFramebuffer::new(320, 240))
+    DisplayServer::new(MockFramebuffer::new(Dimension::new(320), Dimension::new(240)))
 }
 
 #[test]
 fn draw_rect_writes_pixels() {
     let mut server = test_server();
     let resp = server.handle(DisplayRequest::DrawRect {
-        x: 0,
-        y: 0,
-        w: 4,
-        h: 3,
-        color: 0xFF,
+        x: ScreenCoord::new(0),
+        y: ScreenCoord::new(0),
+        w: Dimension::new(4),
+        h: Dimension::new(3),
+        color: Color::from_raw(0xFF),
     });
     assert_eq!(resp, DisplayResponse::Ok);
     assert_eq!(server.framebuffer().pixel_count(), 12);
@@ -25,13 +26,13 @@ fn draw_rect_writes_pixels() {
 fn clear_resets_pixels() {
     let mut server = test_server();
     server.handle(DisplayRequest::DrawRect {
-        x: 0,
-        y: 0,
-        w: 10,
-        h: 10,
-        color: 0xFF,
+        x: ScreenCoord::new(0),
+        y: ScreenCoord::new(0),
+        w: Dimension::new(10),
+        h: Dimension::new(10),
+        color: Color::from_raw(0xFF),
     });
-    server.handle(DisplayRequest::Clear { color: 0 });
+    server.handle(DisplayRequest::Clear { color: Color::from_raw(0) });
     assert_eq!(server.framebuffer().pixel_count(), 0);
 }
 
@@ -50,8 +51,8 @@ fn get_dimensions_returns_size() {
     assert_eq!(
         resp,
         DisplayResponse::Dimensions {
-            width: 320,
-            height: 240
+            width: Dimension::new(320),
+            height: Dimension::new(240),
         }
     );
 }
@@ -60,16 +61,16 @@ fn get_dimensions_returns_size() {
 fn draw_rect_correct_pixel_positions() {
     let mut server = test_server();
     server.handle(DisplayRequest::DrawRect {
-        x: 5,
-        y: 10,
-        w: 2,
-        h: 2,
-        color: 0xAB,
+        x: ScreenCoord::new(5),
+        y: ScreenCoord::new(10),
+        w: Dimension::new(2),
+        h: Dimension::new(2),
+        color: Color::from_raw(0xAB),
     });
     let fb = server.framebuffer();
     assert_eq!(fb.pixel_count(), 4);
-    assert_eq!(fb.pixel_at(0), (5, 10, 0xAB));
-    assert_eq!(fb.pixel_at(1), (6, 10, 0xAB));
-    assert_eq!(fb.pixel_at(2), (5, 11, 0xAB));
-    assert_eq!(fb.pixel_at(3), (6, 11, 0xAB));
+    assert_eq!(fb.pixel_at(0), (ScreenCoord::new(5), ScreenCoord::new(10), Color::from_raw(0xAB)));
+    assert_eq!(fb.pixel_at(1), (ScreenCoord::new(6), ScreenCoord::new(10), Color::from_raw(0xAB)));
+    assert_eq!(fb.pixel_at(2), (ScreenCoord::new(5), ScreenCoord::new(11), Color::from_raw(0xAB)));
+    assert_eq!(fb.pixel_at(3), (ScreenCoord::new(6), ScreenCoord::new(11), Color::from_raw(0xAB)));
 }