fix(simulation): resolve clippy warnings in atlas modules

Replace HashMap/HashSet with BTreeMap/BTreeSet per D-030 determinism
rule. Fix while_let_loop, map_or simplification, collapsible if,
unsigned_abs casting, iterator indexing, and redundant wildcard arms.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/src/atlas/gen_queue.rs

@@ -109,7 +109,7 @@ pub struct GenerationQueue {
     /// Rayon thread pool dedicated to generation work.
     pool: rayon::ThreadPool,
     /// Set of body_ids currently in-flight to avoid duplicate submissions.
-    in_flight: Arc<Mutex<std::collections::HashSet<String>>>,
+    in_flight: Arc<Mutex<std::collections::BTreeSet<String>>>,
 }
 
 impl std::fmt::Debug for GenerationQueue {
@@ -150,7 +150,7 @@ impl GenerationQueue {
             completion_tx: tx,
             completion_rx: rx,
             pool,
-            in_flight: Arc::new(Mutex::new(std::collections::HashSet::new())),
+            in_flight: Arc::new(Mutex::new(std::collections::BTreeSet::new())),
         }
     }
 
@@ -169,7 +169,7 @@ impl GenerationQueue {
             // Check pending list.
             let pending = self.pending.lock().unwrap();
             if pending.iter().any(|q| {
-                q.item.body_id().map_or(false, |id| id == body_id)
+                q.item.body_id() == Some(body_id)
             }) {
                 return;
             }
@@ -193,11 +193,8 @@ impl GenerationQueue {
     /// available without blocking.
     pub fn drain_completions(&self) -> Vec<GenCompletion> {
         let mut out = Vec::new();
-        loop {
-            match self.completion_rx.try_recv() {
-                Ok(c) => out.push(c),
-                Err(_) => break,
-            }
+        while let Ok(c) = self.completion_rx.try_recv() {
+            out.push(c);
         }
         out
     }