core: rewrite panic sites as explicit match+panic

Replace implicit unwrap()/expect() in the lock-ordered core with explicit
match arms. Lock-poison sites use one uniform message
("smarm: <lock> lock poisoned (core corrupt): {e}"); invariant sites panic
with a descriptive message naming the violated invariant. No behaviour
change: each rewrite preserves the prior panic-on-bad-arm semantics. Also
clears the accompanying clippy hygiene in these files (redundant_closure,
len_without_is_empty, too_many_arguments, unnecessary_sort_by,
missing_safety_doc, nonminimal_bool/unnecessary_unwrap).

src/run_queue.rs

@@ -113,16 +113,32 @@ impl MutexQueue {
 
     pub fn push(&self, pid: Pid) {
         assert_no_preempt();
-        self.q.lock().unwrap().push_back(pid);
+        match self.q.lock() {
+            Ok(mut g) => g.push_back(pid),
+            Err(e) => panic!("smarm: run-queue q lock poisoned (core corrupt): {e}"),
+        }
     }
 
     pub fn pop(&self) -> Option<Pid> {
         assert_no_preempt();
-        self.q.lock().unwrap().pop_front()
+        match self.q.lock() {
+            Ok(mut g) => g.pop_front(),
+            Err(e) => panic!("smarm: run-queue q lock poisoned (core corrupt): {e}"),
+        }
     }
 
     pub fn len(&self) -> u64 {
-        self.q.lock().unwrap().len() as u64
+        match self.q.lock() {
+            Ok(g) => g.len() as u64,
+            Err(e) => panic!("smarm: run-queue q lock poisoned (core corrupt): {e}"),
+        }
+    }
+
+    pub fn is_empty(&self) -> bool {
+        match self.q.lock() {
+            Ok(g) => g.is_empty(),
+            Err(e) => panic!("smarm: run-queue q lock poisoned (core corrupt): {e}"),
+        }
     }
 }
 
@@ -262,6 +278,10 @@ impl MpmcRing {
         let d = self.dequeue_pos.0.load(Ordering::Relaxed);
         e.saturating_sub(d) as u64
     }
+
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
 }
 
 // ---------------------------------------------------------------------------
@@ -341,6 +361,10 @@ impl StripedRing {
     pub fn len(&self) -> u64 {
         self.stripes.iter().map(|s| s.len()).sum()
     }
+
+    pub fn is_empty(&self) -> bool {
+        self.stripes.iter().all(|s| s.is_empty())
+    }
 }
 
 // ---------------------------------------------------------------------------