refactor(kernel): split ipc/memory/lib/thread by concern; trim comments

crates/kernel/src/smp.rs

@@ -1,9 +1,5 @@
-//! Cores. Every thread has a home core, chosen when it is created, and
-//! only ever runs there: it waits in that core's run queue and is never
-//! migrated. Making a thread ready from another core sends that core an
-//! IPI when it has to look at its queue again (it is idle, or the thread
-//! outranks what it is running), and so does taking away the thread a
-//! core is running.
+//! Cores: each thread has a home core and never migrates; waking or removing a thread on
+//! another core sends that core an IPI when it must re-check its queue.
 
 use domain::{
     scheduler::{Scheduler, SchedulerDecision},
@@ -88,10 +84,8 @@ impl<P: Platform> Kernel<P> {
         self.threads.get(tid).ok().map(|t| t.priority())
     }
 
-    /// What `core` should do after an IPI: keep running its thread, or
-    /// switch to a higher-priority one now waiting. When it has no thread
-    /// (it was idle, or its thread was destroyed) the caller picks the
-    /// next one itself.
+    /// What `core` does after an IPI: keep its thread or switch to a higher-priority one;
+    /// with no thread the caller picks.
     pub fn reschedule(&mut self, core: CoreId) -> SchedulerDecision {
         let Some(current) = self.scheduler.current(core) else {
             return SchedulerDecision::Continue;