Notify gui-cs/Editor on NuGet publish (#5483)

Dispatches `terminal-gui-published` (payload: the published SemVer) to
gui-cs/Editor after each publish. Editor's bump-terminal-gui.yml picks it
up, pins the new version, validates with its full test suites, and
republishes Editor against it - making Editor a continuous canary for TG
API churn (see Editor specs/decisions.md DEC-010).

No-op until an EDITOR_DISPATCH_TOKEN secret (PAT with repo scope on
gui-cs/Editor) is configured; Editor also polls NuGet on a 6h schedule as
a fallback, so nothing breaks without it.

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Author: tig

.github/workflows/publish.yml

@@ -119,4 +119,20 @@ jobs:
         token: ${{ secrets.TEMPLATE_REPO_TOKEN }}
         repository: gui-cs/Terminal.Gui.templates
         event-type: terminal-gui-v2-released
-        client-payload: ${{ steps.payload.outputs.json }} 
+        client-payload: ${{ steps.payload.outputs.json }}
+
+    # Notify gui-cs/Editor so its bump-terminal-gui.yml workflow can pin the
+    # just-published version, validate, and republish Editor against it
+    # (Editor is the continuous canary for TG API churn — see Editor's
+    # specs/decisions.md DEC-010). Editor also polls NuGet on a schedule, so a
+    # missing token degrades gracefully.
+    # Requires EDITOR_DISPATCH_TOKEN: a PAT with `repo` scope on gui-cs/Editor.
+    - name: Notify gui-cs/Editor of publish
+      if: ${{ secrets.EDITOR_DISPATCH_TOKEN != '' }}
+      continue-on-error: true
+      uses: peter-evans/repository-dispatch@v4
+      with:
+        token: ${{ secrets.EDITOR_DISPATCH_TOKEN }}
+        repository: gui-cs/Editor
+        event-type: terminal-gui-published
+        client-payload: '{"version":"${{ steps.gitversion.outputs.SemVer }}"}'