Fall back to spec retention defaults before the global default

GetRetentionDays previously dropped straight from a missing user
override to RetentionDefaultDays, so every channel showed 30 days
in the UI even though the spec lists 365 for Tells and 90 for own-
conversation channels. Insert a middle layer: user override → spec
default → global default. The retention sweep now seeds its policy
from PrivacyDefaults.DefaultRetentionDays first and lets explicit
user overrides win on top, and the per-channel UI tags each row as
[override], [spec], or [global] so the source of the value is
visible without guessing.

ChatTwo/Plugin.cs

@@ -318,7 +318,12 @@ public sealed class Plugin : IDalamudPlugin
             return;
 
         // Snapshot the policy so the user can edit settings while we run.
-        var policy = Config.RetentionPerChannelDays.ToDictionary(p => (int)(ushort)p.Key, p => p.Value);
+        // Spec defaults form the baseline; explicit user overrides win.
+        var policy = new Dictionary<int, int>();
+        foreach (var (type, days) in Privacy.PrivacyDefaults.DefaultRetentionDays)
+            policy[(int)(ushort)type] = days;
+        foreach (var (type, days) in Config.RetentionPerChannelDays)
+            policy[(int)(ushort)type] = days;
         var defaultDays = Config.RetentionDefaultDays;
 
         new Thread(() =>