Standardize pull request guidance

.github/pull_request_template.md

@@ -0,0 +1,15 @@
+## Background
+
+<!-- Explain the problem or opportunity, the relevant current state, and why this change is needed. -->
+
+## Implementation Approach
+
+<!-- Describe the change, important design decisions, and scope boundaries. Use bullets when appropriate. -->
+
+## Testing Approach
+
+<!-- List the exact automated commands and manual or integration checks performed. State any checks not run and why. -->
+
+## Review Perspectives / Points of Concern
+
+<!-- Direct reviewers to material risks, trade-offs, compatibility, security, performance, accessibility, rollout, or rollback concerns. Write "None" when there are no special concerns. -->

AGENTS.md

@@ -0,0 +1,12 @@
+# Repository Guide
+
+## Language
+
+Write repository content, code comments, commit messages, issues, and pull requests in English.
+
+## Pull Requests
+
+- Use a topic branch and pull request; do not push implementation changes directly to `main`.
+- Write pull request titles and bodies in English.
+- Follow `.github/pull_request_template.md` without removing or renaming its sections, and replace every placeholder with repository-specific content.
+- Run the relevant validation and conformance checks documented by this repository before delivery.