Update template sync workflow and add copilot instructions (#640)

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

Author: edvilme

.github/copilot-instructions.md

@@ -0,0 +1,9 @@
+# Copilot Instructions for vscode-black-formatter
+
+## Development Guidelines
+
+- When introducing new functionality, add basic tests following the existing repo test structure.
+- Always make sure all tests pass before submitting changes.
+- Always ensure documents and code are linted before submitting.
+- Do multiple rounds of review and refinement.
+- Do not feature creep — keep changes focused on the task at hand.

.github/workflows/extension-template-sync.md

@@ -120,7 +120,7 @@ If a file has diverged too much to apply changes confidently, **do not modify it
 
 Use the `create-pull-request` safe output with:
 
-- **Title**: `Sync with template: <original PR title>` (or `Sync with template: <N> recent changes` if combining multiple PRs)
+- **Title**: `Template Sync: <Title of PR>` (if syncing a single PR) or `Template Sync: <Summary>` (if combining multiple PRs)
 - **Body** structured as:
 
 ```
@@ -131,16 +131,21 @@ This PR syncs changes from the upstream [vscode-python-tools-extension-template]
 #### Source PR(s)
 - microsoft/vscode-python-tools-extension-template#<NUMBER> — <title>
 
+#### Related Issues
+<List any issues referenced or fixed by the source PR(s), including cross-repo issues. Omit this section if none.>
+
 #### Changes Applied
 <List of files modified and a brief description of what changed in each.>
 
 #### Files Skipped
 <List of files from the template PR that were skipped and why. Omit this section if none were skipped.>
 
 #### ⚠️ Review Notes
-- This PR was auto-generated by the template sync workflow.
 - Review all changes carefully, especially in files with tool-specific customizations.
 - Run tests locally before merging.
+
+---
+🤖 This PR was auto-generated by the [`extension-template-sync`](.github/workflows/extension-template-sync.md) workflow.
 ```
 
 ### Step 5: Handle edge cases