added contrib and minimal technical coc

CODE_OF_CONDUCT.md

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+# CODE_OF_CONDUCT.md (compact model)
+
+Purpose: Maintain a collaborative, harassment-free environment focused
+on shipping quality software.
+
+Standards:  Be  respectful;  assume  good intent;  no  harassment;  no
+discrimination; keep critiques technical.
+
+Scope: All project spaces (issues, PRs, forums, events).
+
+Reporting: Email tom AT vondein DOT org. Acknowledge within 72 hours.
+
+Enforcement:    Two    maintainers     review,    one    recuses    on
+conflict. Sanctions range from warning  to removal. Summary posted (no
+personal details).
+
+Escalation: If you believe maintainers  handled a report in bad faith,
+escalate to our foundation committee (link) for independent review.