fix(models): Fix GGUF models not appearing in picker after download

**Problem:**
Downloaded GGUF models via Model Manager did not appear in picker until SAM restart.
User had to manually restart to see newly downloaded models.

**Root Cause:**
When downloading via ModelDownloadManager:
1. Model file downloaded and registered in registry (line 406)
2. refreshInstalledModels() called → scanForModels() (line 420)
3. scanForModels() called syncWithRegistry() to detect changes
4. syncWithRegistry() returned FALSE (model already registered in step 1!)
5. Because registryChanges=false, notifications NEVER posted
6. EndpointManager never reloaded, ModelListManager never refreshed
7. Model invisible until restart (when scanForModels runs on init)

**Solution:**
Track actual model list changes in scanForModels():
- Capture model paths before scan (previousModelPaths)
- Capture model paths after scan (currentModelPaths)
- Post notifications if EITHER registry changed OR model paths chang- Post notifications if EITHER registry changed OR model paths chang- Post notifications if EITHe build-debug co- Post notifications if EITHER registry changed OR model paths chang- Post notificate- Post notifications if EITHER registry changed OR model paact- Post notificed- Post notifications if EITHER registry cstart
- Hot reload works as originally intended
- Preserves regis- Preserves regis- Preserves regis- Preserves regis- Preserves r from Local Models redesign (20260108.1)

Author: fewtarius

Sources/APIFramework/LocalModelManager.swift

@@ -168,6 +168,9 @@ public class LocalModelManager {
             return
         }
 
+        /// Track previous model state to detect actual changes
+        let previousModelPaths = Set(cachedModels.map { $0.path })
+        
         var scannedModels: [LocalModel] = []
 
         do {
@@ -240,12 +243,21 @@ public class LocalModelManager {
             /// Sync with registry: register any new models found during scan.
             let registryChanges = syncWithRegistry()
 
-            /// Only post notifications if models actually changed (prevents notification loops)
-            /// This enables hot-reloading when new models are downloaded without spamming
-            if registryChanges {
+            /// Detect if model list actually changed (new models added or models removed)
+            let currentModelPaths = Set(cachedModels.map { $0.path })
+            let modelsChanged = previousModelPaths != currentModelPaths
+            
+            /// Post notifications if registry changed OR actual model list changed
+            /// This fixes the bug where downloaded models were pre-registered, so registryChanges=false
+            /// even though the actual model list changed (new model downloaded)
+            if registryChanges || modelsChanged {
                 NotificationCenter.default.post(name: .localModelsDidChange, object: self)
                 NotificationCenter.default.post(name: .endpointManagerDidUpdateModels, object: self)
-                modelLogger.info("Models changed - posted update notifications")
+                if modelsChanged && !registryChanges {
+                    modelLogger.info("Model list changed (downloaded model) - posted update notifications")
+                } else {
+                    modelLogger.info("Models changed - posted update notifications")
+                }
             }
         } catch {
             modelLogger.error("Failed to scan models directory: \(error.localizedDescription)")