fix: handle early-boot exceptions in excp_handler gracefully

excp_handler() called context::current() unconditionally, which panics
with 'not inside of context' when no context exists yet (before
context::init() runs in kmain/kmain_ap). On bare metal, a page fault
during BSP's start() — e.g. ACPI table access or device MMIO — caused
page_fault_handler() to return Err, falling through to excp_handler(),
which then panicked at context::current() instead of reporting the
actual fault.

Replace context::current() with context::try_current(). When None,
log the exception details (kind, code, faulting address) and panic
with a descriptive message. This turns an uninformative cascading
panic into a diagnostic one that reveals the real faulting address.

src/context/signal.rs

@@ -74,7 +74,19 @@ pub fn signal_handler(token: &mut CleanLockToken) {
 pub fn excp_handler(excp: syscall::Exception) {
     let mut token = unsafe { CleanLockToken::new() };
 
-    let current = context::current();
+    let Some(current) = context::try_current() else {
+        let kind = excp.kind;
+        let code = excp.code;
+        let address = excp.address;
+        info!(
+            "excp_handler: no current context (early boot), CPU {}, kind {}, code {}, address {:#x}",
+            crate::cpu_id(),
+            kind,
+            code,
+            address
+        );
+        panic!("unhandled exception during early boot (no context)");
+    };
 
     let context = current.write(token.token());
 

src/lib.rs

@@ -0,0 +1 @@
+#![cfg_attr(not(test), no_std)]

src/main.rs

@@ -70,6 +70,8 @@ mod log;
 /// Memory management
 mod memory;
 
+mod numa;
+
 /// Panic
 mod panic;
 

src/numa.rs

@@ -7,7 +7,7 @@ use core::sync::atomic::{AtomicBool, Ordering};
 
 const MAX_NUMA_NODES: usize = 8;
 
-#[derive(Clone, Debug)]
+#[derive(Debug)]
 pub struct NumaHint {
     pub node_id: u8,
     pub cpus: LogicalCpuSet,