[chore/github]: Standardize GitHub PR description template

Replace legacy templates with unified pull_request_template.md
(description, type, approach, documentation).

Signed-off-by: Oleksandr Ivantsiv <oivantsiv@nvidia.com>

Author: oleksandrivantsiv

.github/copilot-instructions.md

@@ -112,6 +112,11 @@ def test_my_config_command():
 - **Testing**: All new commands MUST have unit tests
 - **Backwards compatibility**: Don't break existing CLI command syntax
 - **Yang validation**: New config commands should validate against YANG models
+- **PR description template**: Fill out all sections of the [PR template](.github/pull_request_template.md) when submitting a pull request:
+  - **Description of PR**: Summary of the change, motivation/context, reviewer entry point, and dependencies; reference issues with `fixes #xxxx` / `closes #xxxx`.
+  - **Type of change**: Mark the box(es) that apply — bug fix, new feature, refactor / cleanup, documentation update, test improvement.
+  - **Approach**: Motivation; how you did it; how you verified/tested it; any platform-specific notes.
+  - **Documentation**: Link to wiki / doc updates relevant to new features or test cases.
 
 ## Common Patterns
 

.github/pull_request_template.md

@@ -1,32 +1,45 @@
 <!--
-    Please make sure you've read and understood our contributing guidelines:
-    https://github.com/Azure/SONiC/blob/gh-pages/CONTRIBUTING.md
+Please make sure you've read and understood our contributing guidelines;
+https://github.com/Azure/SONiC/blob/gh-pages/CONTRIBUTING.md
 
-    ** Make sure all your commits include a signature generated with `git commit -s` **
-
-    If this is a bug fix, make sure your description includes "closes #xxxx",
-    "fixes #xxxx" or "resolves #xxxx" so that GitHub automatically closes the related
-    issue when the PR is merged.
+Please provide following information to help code review process a bit easier:
+-->
+### Description of PR
+<!--
+- Please include a summary of the change and which issue is fixed.
+- Please also include relevant motivation and context. Where should reviewer start? background context?
+- List any dependencies that are required for this change.
+-->
 
-    If you are adding/modifying/removing any command or utility script, please also
-    make sure to add/modify/remove any unit tests from the tests
-    directory as appropriate.
+Summary:
+Fixes # (issue)
 
-    If you are modifying or removing an existing 'show', 'config' or 'sonic-clear'
-    subcommand, or you are adding a new subcommand, please make sure you also
-    update the Command Line Reference Guide (doc/Command-Reference.md) to reflect
-    your changes.
+### Type of change
 
-    Please provide the following information:
+<!--
+- Fill x for your type of change.
+- e.g.
+- [x] Bug fix
 -->
 
-#### What I did
+- [ ] Bug fix
+- [ ] New feature
+- [ ] Refactor / cleanup
+- [ ] Documentation update
+- [ ] Test improvement
 
-#### How I did it
+### Approach
+#### What is the motivation for this PR?
 
-#### How to verify it
+#### How did you do it?
 
-#### Previous command output (if the output of a command-line utility has changed)
+#### How did you verify/test it?
 
-#### New command output (if the output of a command-line utility has changed)
+#### Any platform specific information?
 
+### Documentation
+<!--
+(If it's a new feature, new test case)
+Did you update documentation/Wiki relevant to your implementation?
+Link to the wiki page?
+-->