docs: add CODE_OF_CONDUCT.md file

Add Contributor Covenant Code of Conduct to establish community standards and enforcement procedures

CODE_OF_CONDUCT.md

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+# Contributor Covenant Code of Conduct
+
+## Our Pledge
+
+We pledge to make participation in CogniXpert v1.0 a harassment‑free experience for everyone, regardless of age, body size, disability, ethnicity, gender identity and expression, level of experience, nationality, personal appearance, race, religion, or sexual identity and orientation.
+
+## Our Standards
+
+- Use welcoming and inclusive language
+- Respect differing viewpoints and experiences
+- Gracefully accept constructive criticism
+- Focus on what is best for the community
+- Show empathy towards others
+
+## Unacceptable Behavior
+
+- Harassment, bullying, or discrimination
+- Publishing others’ private information
+- Disruptive or derogatory comments
+- Other conduct which could reasonably be considered inappropriate
+
+## Responsibilities
+
+Maintainers are responsible for clarifying standards and taking appropriate and fair corrective action in response to unacceptable behavior.
+
+## Scope
+
+This Code applies within project spaces and in public spaces when an individual is representing the project.
+
+## Enforcement
+
+Report issues to: `hello@cogni-x.com` (or open a confidential issue). All complaints will be reviewed and investigated.
+
+## Attribution
+
+Adapted from the [Contributor Covenant](https://www.contributor-covenant.org) v2.1.
+