kernel: fix post-merge compile errors (import dedup + UnmapVec)

Two fixes required for the merged tree to compile (repo cook kernel
--force-rebuild passes with them):

- event.rs: drop EAGAIN/EINTR from the top-level syscall import — the
  crate::syscall::error import further down already brings both names
  into scope (E0252 duplicate-definition).

- scheme/proc.rs: drop UnmapVec from the context::memory import — the
  fork deleted that machinery from context/memory.rs (E0432
  unresolved import); the type's only use site is the import itself.

src/event.rs

@@ -2,7 +2,7 @@ use alloc::sync::Arc;
 use core::sync::atomic::{AtomicUsize, Ordering};
 use hashbrown::{hash_map::DefaultHashBuilder, HashMap};
 use smallvec::SmallVec;
-use syscall::{data::GlobalSchemes, EAGAIN, EINTR};
+use syscall::data::GlobalSchemes;
 
 use crate::{
     context,

src/scheme/proc.rs

@@ -3,7 +3,7 @@ use crate::{
         self,
         context::{HardBlockedReason, LockedFdTbl, SignalState},
         file::InternalFlags,
-        memory::{handle_notify_files, AddrSpace, AddrSpaceWrapper, Grant, PageSpan, UnmapVec},
+        memory::{handle_notify_files, AddrSpace, AddrSpaceWrapper, Grant, PageSpan},
         unblock_context, wakeup_context, Context, ContextLock, Status,
     },
     memory::{Page, VirtualAddress, PAGE_SIZE},