update CONTRIBUTING.md

.github/CONTRIBUTING.md

@@ -6,10 +6,32 @@ Thank you for your interest in contributing to VRCX! Here are a few guidelines t
 
 - **Large changes require prior discussion.** If your PR involves significant new features, refactors, or architectural changes, please open an issue first to discuss the approach. PRs submitted without prior discussion may not be accepted.
 - **Small fixes are always welcome.** Typo fixes, bug fixes, and minor improvements can be submitted directly.
+- **UI-related PRs will most likely be declined.** To maintain a consistent and cohesive user interface, PRs that modify UI elements (layouts, styling, visual components, etc.) are generally not accepted. If you have a UI suggestion or improvement idea, please [Open an issue](https://github.com/vrcx-team/VRCX/issues/new) instead so we can discuss it with the team.
+
+## Important Considerations
+
+### International User Base
+
+VRCX is used by a diverse, international community with users from many different countries and cultures. Before submitting a PR, please consider:
+
+- **Is this feature broadly useful and valuable?** Niche or low-value features increase maintenance burden without proportional benefits and may not be accepted.
+- **Could it negatively impact other features?** Changes that interfere with or degrade existing functionality will not be merged.
+
+Please think carefully about these factors before investing time in a contribution.
+
+### Performance Design Baseline
+
+VRCX is designed to perform well for users with **1,000 to 4,000 friends**. For any changes involving data operations, the design should be able to handle databases up to **8 GB** in size. Please keep these baselines in mind when implementing features or optimizations.
+
+**PRs that do not follow these guidelines may be closed without review.**
 
 ## Looking for Something to Work On?
 
-Check out issues labeled [`PR welcome`](https://github.com/vrcx-team/VRCX/issues?q=label%3A%22pr+welcome%22+is%3Aclosed) — these are contributions we'd love to see. Note that even for `PR welcome` issues, if the change involves core functionality, please discuss it in the issue first.
+Check out issues labeled [`PR welcome`](https://github.com/vrcx-team/VRCX/issues?q=label%3A%22pr+welcome%22+is%3Aclosed) — these are contributions we'd love to see.
+
+- These issues are listed under **Closed** issues, not Open, so make sure to check the closed tab. We keep them in Closed to avoid cluttering the Open issues list.
+- You can link the issue in your PR, and once merged, we will mark the issue as completed.
+- Even for `PR welcome` issues, if the change involves core functionality, please discuss it in the issue first.
 
 ## Submitting a Pull Request