CI: AppVeyor: Branch builds only for main and release tags

AGENTS.md

@@ -189,7 +189,7 @@ The website is deployed to GitHub Pages at: https://borntoberoot.net/NETworkMana
   architecture, only for tags). PRs only build the application (`NETworkManager.csproj`) unless they change
   `Source/NETworkManager.Setup/`, branches and tags the setup (`NETworkManager.Setup.wixproj`)
 - Runs the unit tests (`Source/NETworkManager.Tests`, `dotnet test --project`)
-- Branches with an open PR are only built as PR (`skip_branch_with_pr`)
+- Branch builds only for `main` and release tags (`branches: only`), other branches are only built as PR
 - Ends successfully without building if only docs / website / repository files changed (`Website/`, `.github/`,
   `.claude/`, `Images/`, `Chocolatey/`, `WinGet/`, `Tests/Environments/`, `*.md`, `LICENSE`), so Mergify still gets a
   green status. Tags are always built. Branch builds (e.g. `main`) only see the last commit, so they are only skipped

appveyor.yml

@@ -9,8 +9,13 @@ environment:
 # Shallow clone - the history isn't needed (the version is date based). Must stay > 1, the docs-only check below
 # compares HEAD with HEAD~1.
 clone_depth: 50
-# Branches with an open PR are built as PR (merge commit) only - Mergify waits for that status.
-skip_branch_with_pr: true
+# Branch builds only for main and release tags (e.g. 2026.10.24.0 - the filter also applies to tag names). Other
+# branches are only built as PR (merge commit), Mergify waits for that status. skip_branch_with_pr is not enough, the
+# first push of a branch (e.g. by Dependabot) is built before the PR exists. PRs to main are not affected by "only".
+branches:
+  only:
+    - main
+    - /^\d+\.\d+\.\d+/
 install:
   - ps: |
       # Skip the build if only docs / website / repository files changed. Exit-AppveyorBuild ends the build