feat: proper IPC-based boot — init loads servers from storage via IPC, VirtIO GPU driver

Complete microkernel boot pipeline: adapter loads only init + storage + display
from disk. Init bootstraps all other servers by reading binaries from the
storage server via IPC, parsing ELF, creating processes, mapping pages, and
spawning threads.

New syscalls:
- CreateEndpoint: userspace endpoint creation with full capability grant
- DebugPutchar: debug output to UART from userspace
- MapPage: cross-process page mapping (init loads binaries into children)
- SpawnThreadIn: spawn thread in another process via capability

Key fixes:
- Per-process L1 page tables for VPN[2]=0 (prevents cross-process corruption)
- Separate kernel_pt from page_tables[0] (init pid=0 overwrote kernel PT ref)
- Thread Running state set in switch_to_next (syscalls rejected without it)
- Pending IPC results applied during context switch
- SIE disabled during boot (timer can't preempt into unready processes)
- User heap VA starts at 0x40000 (avoids shared buffer at 0x30000)
- RequestPages maps at user VAs via per-process heap allocator

VirtIO GPU:
- Adapter probes for GPU device, initializes resource/scanout/backing
- Display server writes to mapped framebuffer, flushes via GPU virtqueue
- 640x480 BGRA framebuffer with transfer-to-host and resource-flush

Storage server:
- Userspace VirtIO block driver using pre-mapped MMIO and DMA pages
- FAT16 filesystem reader serving file-read requests via IPC
- Shared buffer protocol: init writes filename, storage writes file data

Echo app for IPC testing (adapter-loaded echo proved the pipeline end-to-end).

crates/init/src/manifest.rs

@@ -1,112 +0,0 @@
-use types::address::PhysicalAddress;
-use types::bounded::Priority;
-use types::id::IrqId;
-
-#[derive(Debug, Clone, Copy)]
-pub enum HardwareCap {
-    Framebuffer { base: PhysicalAddress, pages: usize },
-    Irq { irq: IrqId },
-    Memory { base: PhysicalAddress, pages: usize },
-}
-
-#[derive(Debug, Clone, Copy)]
-pub enum EndpointBinding {
-    Own { name: &'static str },
-    ConnectTo { server: &'static str, endpoint: &'static str },
-}
-
-#[derive(Debug, Clone, Copy)]
-pub enum BinarySource {
-    Ram { base: PhysicalAddress, size: usize },
-    Storage { path: &'static str },
-}
-
-#[derive(Debug)]
-pub struct ServerEntry {
-    pub name: &'static str,
-    pub priority: Priority,
-    pub memory_pages: usize,
-    pub hardware_caps: &'static [HardwareCap],
-    pub endpoints: &'static [EndpointBinding],
-    pub restartable: bool,
-    pub binary: BinarySource,
-}
-
-#[derive(Debug)]
-pub struct BootManifest {
-    pub servers: &'static [ServerEntry],
-}
-
-pub static SNAKE_MANIFEST: BootManifest = BootManifest {
-    servers: &[
-        ServerEntry {
-            name: "log",
-            priority: Priority::DEFAULT,
-            memory_pages: 64,
-            hardware_caps: &[],
-            endpoints: &[EndpointBinding::Own { name: "log" }],
-            restartable: true,
-            binary: BinarySource::Storage { path: "/servers/log.elf" },
-        },
-        ServerEntry {
-            name: "permission",
-            priority: Priority::DEFAULT,
-            memory_pages: 32,
-            hardware_caps: &[],
-            endpoints: &[EndpointBinding::Own { name: "permission" }],
-            restartable: true,
-            binary: BinarySource::Storage { path: "/servers/permission.elf" },
-        },
-        ServerEntry {
-            name: "storage",
-            priority: Priority::DEFAULT,
-            memory_pages: 128,
-            hardware_caps: &[],
-            endpoints: &[EndpointBinding::Own { name: "storage" }],
-            restartable: true,
-            binary: BinarySource::Ram {
-                base: PhysicalAddress::from_raw(0),
-                size: 0,
-            },
-        },
-        ServerEntry {
-            name: "display",
-            priority: Priority::DEFAULT,
-            memory_pages: 256,
-            hardware_caps: &[
-                HardwareCap::Framebuffer {
-                    base: PhysicalAddress::from_raw(0x10008000),
-                    pages: 75,
-                },
-            ],
-            endpoints: &[EndpointBinding::Own { name: "display" }],
-            restartable: true,
-            binary: BinarySource::Storage { path: "/servers/display.elf" },
-        },
-        ServerEntry {
-            name: "input",
-            priority: Priority::DEFAULT,
-            memory_pages: 32,
-            hardware_caps: &[
-                HardwareCap::Irq { irq: IrqId::from_raw(10) },
-            ],
-            endpoints: &[EndpointBinding::Own { name: "input" }],
-            restartable: true,
-            binary: BinarySource::Storage { path: "/servers/input.elf" },
-        },
-        ServerEntry {
-            name: "session",
-            priority: Priority::DEFAULT,
-            memory_pages: 64,
-            hardware_caps: &[],
-            endpoints: &[
-                EndpointBinding::Own { name: "session" },
-                EndpointBinding::ConnectTo { server: "display", endpoint: "display" },
-                EndpointBinding::ConnectTo { server: "input", endpoint: "input" },
-                EndpointBinding::ConnectTo { server: "storage", endpoint: "storage" },
-            ],
-            restartable: true,
-            binary: BinarySource::Storage { path: "/servers/session.elf" },
-        },
-    ],
-};