Dependencies: add PublishesFromReleaseBranch; set on Metalama.Vsx

Adds an init-only PublishesFromReleaseBranch flag on DependencyDefinition.
PublishingBranch now resolves to ReleaseBranch when either the family has
a consolidated product (existing rule) OR this flag is set.

Set the flag in both MetalamaVsxDependencies.V2026_0 and V2026_1: Vsx
publishes from release/<version> rather than develop/<version> even
though it has no consolidated product, so its TC deployment branch and
PublishCommand checkout target now resolve to the release branch.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: PostSharpAgent

src/PostSharp.Engineering.BuildTools/Dependencies/Definitions/MetalamaVsxDependencies.V2026_0.cs

@@ -49,7 +49,10 @@ public MetalamaVsxDependencyDefinition(
                         isVersioned,
                         pullRequestRequiresStatusCheck: pullRequestRequiresStatusCheck,
                         vcsRootProjectId: vcsRootProjectId ),
-                    isVersioned ) { }
+                    isVersioned )
+            {
+                this.PublishesFromReleaseBranch = true;
+            }
         }
 
         public static ProductFamily Family { get; } = new( _projectName, "2026.0", DevelopmentDependencies.Family, MetalamaDependencies.V2026_0.Family )

src/PostSharp.Engineering.BuildTools/Dependencies/Definitions/MetalamaVsxDependencies.V2026_1.cs

@@ -49,7 +49,10 @@ public MetalamaVsxDependencyDefinition(
                         isVersioned,
                         pullRequestRequiresStatusCheck: pullRequestRequiresStatusCheck,
                         vcsRootProjectId: vcsRootProjectId ),
-                    isVersioned ) { }
+                    isVersioned )
+            {
+                this.PublishesFromReleaseBranch = true;
+            }
         }
 
         public static ProductFamily Family { get; } = new( _projectName, "2026.1", DevelopmentDependencies.Family, MetalamaDependencies.V2026_1.Family )

src/PostSharp.Engineering.BuildTools/Dependencies/Model/DependencyDefinition.cs

@@ -47,9 +47,19 @@ public class DependencyDefinition
         /// </remarks>
         public string? ReleaseBranch { get; }
 
-        // If the product is part of a consolidated build, pre-publishing takes place and the deployment is preformed from the release branch.
-        // If not, the deployment is performed from the default branch, and post-publishing is is part of the publishing step.
-        public string PublishingBranch => this.ReleaseBranch != null && this.ProductFamily.HasConsolidatedProduct ? this.ReleaseBranch : this.Branch;
+        /// <summary>
+        /// Forces <see cref="PublishingBranch"/> to resolve to <see cref="ReleaseBranch"/> for products that publish from
+        /// the release branch even though they are not part of a consolidated build (e.g. Metalama.Vsx).
+        /// </summary>
+        public bool PublishesFromReleaseBranch { get; init; }
+
+        // If the product is part of a consolidated build, pre-publishing takes place and the deployment is performed from the release branch.
+        // If not, the deployment is performed from the default branch, and post-publishing is part of the publishing step.
+        // Products with PublishesFromReleaseBranch = true also publish from the release branch even without a consolidated build.
+        public string PublishingBranch
+            => this.ReleaseBranch != null && (this.ProductFamily.HasConsolidatedProduct || this.PublishesFromReleaseBranch)
+                ? this.ReleaseBranch
+                : this.Branch;
 
         public CiProjectConfiguration CiConfiguration { get; }