fix(simulation): Clippy cleanup and CI enforcement (#635)

Fix all Clippy warnings across the server codebase (2411 insertions, 1341
deletions). Raise type-complexity-threshold to 750 and too-many-arguments
to 12 in .clippy.toml for idiomatic Bevy ECS system signatures. The server
now passes `cargo clippy -- --deny warnings` cleanly.

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

server/src/voice/cache.rs

@@ -103,10 +103,7 @@ impl VoiceCacheStore {
     pub fn zone_cache(&mut self, zone_id: u32) -> &mut ZoneVoiceCache {
         if !self.zones.contains_key(&zone_id) {
             let cache = self.load_zone(zone_id).unwrap_or_else(|| {
-                ZoneVoiceCache::new(
-                    self.model_version.clone(),
-                    self.injector_version.clone(),
-                )
+                ZoneVoiceCache::new(self.model_version.clone(), self.injector_version.clone())
             });
             self.zones.insert(zone_id, cache);
         }
@@ -139,8 +136,7 @@ impl VoiceCacheStore {
         fs::create_dir_all(&dir)?;
 
         let path = dir.join(format!("{}.msgpack", zone_id));
-        let data = rmp_serde::to_vec(cache)
-            .map_err(|e| io::Error::new(io::ErrorKind::Other, e))?;
+        let data = rmp_serde::to_vec(cache).map_err(io::Error::other)?;
         fs::write(path, data)
     }
 
@@ -163,10 +159,7 @@ impl VoiceCacheStore {
         if cache.model_version != self.model_version
             || cache.injector_version != self.injector_version
         {
-            tracing::info!(
-                zone_id,
-                "voice cache version mismatch — invalidating"
-            );
+            tracing::info!(zone_id, "voice cache version mismatch — invalidating");
             return None;
         }
 
@@ -286,7 +279,10 @@ mod tests {
 
         let data = rmp_serde::to_vec(&cache).unwrap();
         let restored: ZoneVoiceCache = rmp_serde::from_slice(&data).unwrap();
-        assert_eq!(restored.lookup(&key), Some("Hands are steady. Eyes aren't."));
+        assert_eq!(
+            restored.lookup(&key),
+            Some("Hands are steady. Eyes aren't.")
+        );
         assert_eq!(restored.model_version, "v1");
     }