chore(repo): initialize Cowork Local Gitea repository

security/attachment_validator.py

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+"""Attachment validator — inspects attached files for security risks."""
+from __future__ import annotations
+
+from .command_risk_classifier import classify_attachment
+
+ATTACHMENT_DENIED_MESSAGE = "Attached content failed security validation."
+
+
+def validate_attachment(path: str, mime_type: str = "") -> bool:
+    result = classify_attachment(path, mime_type or None)
+    return not result.blocked