docs: add Code of Conduct

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CODE_OF_CONDUCT.md

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+Code of Conduct
+
+Our Goal
+
+The goal of this project is to build useful software in a collaborative, respectful environment. Everyone participating in this project—maintainers, contributors, and users—is expected to treat others with basic respect.
+
+You don’t have to agree with everyone, but you do have to act like a reasonable adult.
+
+⸻
+
+Expected Behavior
+
+Please:
+	•	Be respectful and constructive in discussions
+	•	Assume good intentions from other contributors
+	•	Provide helpful feedback instead of personal criticism
+	•	Focus on improving the project
+
+Healthy technical disagreement is normal and encouraged. Personal attacks are not.
+
+⸻
+
+Unacceptable Behavior
+
+The following behavior is not acceptable in project spaces:
+	•	Harassment or personal attacks
+	•	Hate speech or discrimination
+	•	Threats or intimidation
+	•	Deliberate disruption of discussions or development
+	•	Publishing someone else’s private information without permission
+
+If you wouldn’t say it in a professional technical meeting, don’t say it here.
+
+⸻
+
+Enforcement
+
+Project maintainers have the final say on acceptable behavior in this repository.
+
+Maintainers may remove comments, issues, or contributions that violate this Code of Conduct. Repeated or serious violations may result in temporary or permanent bans from participating in the project.
+
+⸻
+
+Scope
+
+This Code of Conduct applies to all project spaces, including:
+	•	GitHub issues
+	•	Pull requests
+	•	Discussions
+	•	Project documentation and comments
+
+⸻
+
+Reporting Issues
+
+If you encounter behavior that violates this Code of Conduct, please open an issue or contact the maintainers.
+
+Reports will be reviewed and handled fairly.
+
+⸻
+
+In Short
+
+Be respectful.
+Be constructive.
+Don’t be a jerk.
+