Add validations for new PRs

.github/copilot-instructions.md

@@ -0,0 +1,18 @@
+# GitHub Copilot custom instructions for assistant_core contributors
+# This file provides guidance to GitHub Copilot (and human reviewers) about
+# repository conventions and PR requirements.
+
+project: assistant_core
+
+instructions:
+  - When suggesting code changes or PR descriptions, ensure the contributor adds
+    a concise CHANGELOG.md entry under the NEXT section that explains what
+    changed and why.
+
+  - Remind contributors to follow `CONTRIBUTING.md`:
+    - Run tests and add tests for behavior changes.
+    - Run formatters and linters (make format / make lint).
+    - Update documentation where applicable.
+
+  - If the suggestion touches public APIs or behavior, encourage adding
+    typed signatures and small unit tests.

.github/pull_request_template.md

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+<!--
+Use this template for new pull requests. It codifies the conventions in CONTRIBUTING.md
+and makes it easy for reviewers to see what's required.
+-->
+
+## Description
+
+A short description of the change. Link to any relevant issue(s) or RFC.
+
+## Type of change
+- [ ] Bugfix
+- [ ] New feature
+- [ ] Documentation update
+- [ ] Refactor
+- [ ] Chore
+
+## Checklist
+Please run through the checklist and mark the items off before requesting review. These mirror the project's `CONTRIBUTING.md` guidelines.
+
+- [ ] Tests added/updated for changes in behavior
+- [ ] Linter/formatter run (make format / make lint)
+- [ ] Documentation updated (if applicable)
+- [ ] CHANGELOG.md updated with a short entry describing the change (Required)
+
+If your change requires special setup or steps to verify, include them below.
+
+## How to test
+Describe steps to reproduce or to run the test suite for the change.
+
+## Additional context
+Any additional information for reviewers, e.g. performance notes or tradeoffs.

CHANGELOG.md

@@ -1,6 +1,7 @@
 # CHANGELOG
 
 ## NEXT
+* Add validation for new PRs
 * Add a builder that adds a prompt with the date and time
 * Add option to control entry point on builder
 * OpenAI responses API is enabled by default