fix(updates): Wire up development channel filtering in Sparkle

**Problem:**
- Users with development updates enabled could see dev releases in the appcast
- BUT Sparkle was filtering them out because allowed channels weren't configured
- The 'Receive development updates' switch changed the feed URL but didn't tell Sparkle to accept development channel items

**Root Cause:**
Missing implementation of Sparkle's `allowedChannels(for:)` delegate method. Without this, Sparkle filters out any items tagged with `<sparkle:channel>development</sparkle:channel>`, even if they're in the feed.

**Solution:**
1. Added `cachedAllowedChannels` property to AppDelegate
2. Implemented `allowedChannels(for:)` SPUUpdaterDelegate method
3. Update `cachedAllowedChannels` when feed URL changes:
   - Development enabled: Set to ["development"]
   - Development disabled: Set to [] (stable only)

**Testing:**
✅ Build: PASS (no errors, warnings only)
✅ Manual: Toggling development updates now correctly shows/hides dev releases
✅ User confirmed: Can switch back and forth, sees d✅ User co26✅ User confirmed: Can switch back and forth, sees d✅ User co26✅ User coers can opt into pre-release testing.

Author: fewtarius

Resources/whats-new.json

@@ -1,8 +1,8 @@
 {
   "releases": [
     {
-      "version": "20260114.1",
-      "release_date": "January 14, 2026",
+      "version": "20260113.1",
+      "release_date": "January 13, 2026",
       "introduction": "This release introduces LoRA fine-tuning capabilities, allowing you to train custom adapters that specialize local models on your own knowledge domains without modifying the base model weights.",
       "highlights": [
         {

Sources/SAM/AppDelegate.swift

@@ -14,6 +14,9 @@ class AppDelegate: NSObject, NSApplicationDelegate, SPUUpdaterDelegate {
     private var windowFrameObserver: NSObjectProtocol?
     private var configuredWindows: Set<ObjectIdentifier> = []
     private let logger = Logger(label: "com.sam.appdelegate")
+    
+    /// Cached allowed channels for Sparkle updates
+    private var cachedAllowedChannels: Set<String> = []
 
     /// Shared instance for accessing updater from Commands.
     nonisolated(unsafe) static weak var shared: AppDelegate?
@@ -90,6 +93,11 @@ class AppDelegate: NSObject, NSApplicationDelegate, SPUUpdaterDelegate {
     func updater(_ updater: SPUUpdater, didFinishLoading appcast: SUAppcast) {
         NSLog("SPARKLE: Finished loading appcast with \(appcast.items.count) items")
     }
+    
+    /// Sparkle delegate method to specify allowed channels
+    func allowedChannels(for updater: SPUUpdater) -> Set<String> {
+        return cachedAllowedChannels
+    }
 
     func applicationShouldTerminateAfterLastWindowClosed(_ sender: NSApplication) -> Bool {
         /// Keep app running when last window is closed (standard macOS behavior).
@@ -234,7 +242,18 @@ class AppDelegate: NSObject, NSApplicationDelegate, SPUUpdaterDelegate {
 
         updaterController.updater.setFeedURL(feedURL)
 
-        logger.info("Sparkle feed URL updated to: \(developmentEnabled ? "development" : "stable") (\(feedURL.absoluteString))")
+        // Configure allowed channels based on development preference
+        if developmentEnabled {
+            // Allow development channel items (tagged with <sparkle:channel>development</sparkle:channel>)
+            cachedAllowedChannels = ["development"]
+            logger.info("Sparkle feed URL updated to: development (\(feedURL.absoluteString))")
+            logger.info("Allowed channels: [development]")
+        } else {
+            // Only show stable releases (items without channel tag)
+            cachedAllowedChannels = []
+            logger.info("Sparkle feed URL updated to: stable (\(feedURL.absoluteString))")
+            logger.info("Allowed channels: [] (stable only)")
+        }
 
         // Check for updates immediately after switching feeds
         if developmentEnabled {