Narrow stable pipeline tag trigger to v* pattern (#1002)

* Bump version to 2026.4.0

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Add PR guidelines to copilot-instructions.md

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Fix stable pipeline trigger to only use tags

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Update release agent: tags-only trigger

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Narrow stable pipeline tag trigger to v* pattern

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: bschnurr

.github/agents/release.agent.md

@@ -18,7 +18,7 @@ Start by reading `package.json` to determine the current version. Then confirm w
 
 - **Even minor** = stable release (e.g. `2026.4.0` — *example*)
 - **Odd minor** = pre-release / dev (e.g. `2026.3.0-dev`, `2026.5.0-dev` — *examples*)
-- The stable release pipeline (`build/azure-devdiv-pipeline.stable.yml`) triggers on git tags matching `refs/tags/*`
+- The stable release pipeline (`build/azure-devdiv-pipeline.stable.yml`) triggers on git tags matching `v*`
 - Tag format: `v<version>` (e.g. `v2026.4.0` — *example*)
 - Release branch format: `release/<YYYY>.<EVEN_MINOR>` (e.g. `release/2026.4` — *example*)
 

build/azure-devdiv-pipeline.stable.yml

@@ -1,10 +1,7 @@
 name: Publish Release
 trigger:
-  branches:
-    include:
-      - release*
   tags:
-    include: ['*']
+    include: ['v*']
 pr: none
 
 resources: