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/drivers/block/virtio/Cargo.toml

@@ -6,3 +6,4 @@ edition = "2024"
 [dependencies]
 port-block-device = { workspace = true }
 hw-virtio = { workspace = true }
+types = { workspace = true }

crates/drivers/block/virtio/src/lib.rs

@@ -4,6 +4,7 @@ use hw_virtio::mmio::MmioAccess;
 use hw_virtio::queue::{QueueAddrs, VirtioQueue};
 use hw_virtio::block::{self, DmaAddrs};
 use port_block_device::{BlockDevice, SectorId};
+use types::address::{PhysicalAddress, VirtualAddress};
 
 const MMIO_BASE: usize = 0x20000;
 const VQUEUE_VA: usize = 0x21000;
@@ -35,19 +36,19 @@ impl VirtioBlockDevice {
         let (hdr_pa, status_pa, data_pa) = unsafe {
             let p = PHYSINFO_VA as *const u64;
             (
-                core::ptr::read_volatile(p),
-                core::ptr::read_volatile(p.add(1)),
-                core::ptr::read_volatile(p.add(2)),
+                core::ptr::read_volatile(p) as usize,
+                core::ptr::read_volatile(p.add(1)) as usize,
+                core::ptr::read_volatile(p.add(2)) as usize,
             )
         };
 
         let dma = DmaAddrs {
-            header_pa: hdr_pa,
-            header_va: REQ_HDR_VA,
-            status_pa,
-            status_va: REQ_HDR_VA + 16,
-            data_pa,
-            data_va: REQ_HDR_VA + 32,
+            header_pa: PhysicalAddress::from_raw(hdr_pa),
+            header_va: VirtualAddress::from_raw(REQ_HDR_VA),
+            status_pa: PhysicalAddress::from_raw(status_pa),
+            status_va: VirtualAddress::from_raw(REQ_HDR_VA + 16),
+            data_pa: PhysicalAddress::from_raw(data_pa),
+            data_va: VirtualAddress::from_raw(REQ_HDR_VA + 32),
         };
 
         Self { mmio: UserMmio, queue, dma }