Merge origin/main into claude/spelunk-tunnel

Port forwarding took host schema version 8 first, so the Spelunk route moves to 9 and is written after the forwards. A host may carry both.

src/DodoSSH.Client.Domain/HostSecretMerge.cs

@@ -99,6 +99,8 @@ public static class HostSecretMerge
             TagIds = MergeTags(ancestor.TagIds, local.TagIds, remote.TagIds, conflicts),
             PinnedPaths = MergePinnedPaths(
                 ancestor.PinnedPaths, local.PinnedPaths, remote.PinnedPaths, conflicts),
+            PortForwards = MergePortForwards(
+                ancestor.PortForwards, local.PortForwards, remote.PortForwards, conflicts),
             RelayEnabled = Field(
                 nameof(HostSecret.RelayEnabled),
                 ancestor.RelayEnabled,
@@ -354,6 +356,46 @@ public static class HostSecretMerge
         return PinnedPathList.Create(merge.Merged.Keys);
     }
 
+    /// <summary>
+    /// Merges the forwards per forward, so two people each adding one both keep theirs.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// Keyed by id and ordered the way <see cref="MergePinnedPaths"/> is: existing forwards, then this
+    /// machine's additions, then the server's.
+    /// </para>
+    /// <para>
+    /// <b>Unlike a tag or a pinned path, a conflict is reachable here.</b> The value under a key is the whole
+    /// rule, so two machines changing one forward differently is a genuine clash. The server's version wins,
+    /// as every scalar's does, and the other is recorded in OpenSSH's notation so the user can read what was
+    /// lost. An edit on one side beats a removal on the other, which is the map merge's standing rule.
+    /// </para>
+    /// </remarks>
+    private static PortForwardList MergePortForwards(
+        PortForwardList ancestor,
+        PortForwardList local,
+        PortForwardList remote,
+        List<HostFieldConflict> conflicts)
+    {
+        var merge = ThreeWayMerge.Map(
+            ancestor.ToIdMap(),
+            local.ToIdMap(),
+            remote.ToIdMap(),
+            EqualityComparer<Guid>.Default);
+
+        foreach (var conflict in merge.Conflicts)
+        {
+            conflicts.Add(new HostFieldConflict(
+                $"{nameof(HostSecret.PortForwards)}[{conflict.Key}]",
+                conflict.DiscardedSide,
+                conflict.Kept?.Notation ?? "removed",
+                conflict.Discarded?.Notation ?? "removed",
+                conflict.DiscardedWasRemoval));
+        }
+
+        return PortForwardList.Create(merge.Merged.Values);
+    }
+
     private static string FormatChain(JumpChain chain) =>
         chain.Count == 0 ? "(none)" : string.Join(" → ", chain);
 }