Preserve preview harness, editor, email and task improvements

Snapshot current maintainer-preview application changes and regression fixtures for integration into lab. Excludes local runtime data, evaluation outputs and source backups. Focused Python regression selection: 140 passed; full suite not certified.

core/auth.py

@@ -465,6 +465,19 @@ class AuthManager:
         logger.info("Set is_admin=%s for '%s' (by '%s')", is_admin, username, requesting_user)
         return SetAdminResult.OK
 
+    def reset_user_password(self, username: str, new_password: str, requesting_user: str) -> bool:
+        """Allow an admin to reset a non-admin account and revoke its sessions."""
+        username = username.strip().lower()
+        with self._config_lock:
+            target = self.users.get(username)
+            if not self.is_admin(requesting_user) or not target or target.get("is_admin"):
+                return False
+            self._config["users"][username]["password_hash"] = _hash_password(new_password)
+            self._save()
+            self.revoke_user_sessions(username)
+        logger.info("Password reset for '%s' by '%s'", username, requesting_user)
+        return True
+
     def change_password(self, username: str, current_password: str, new_password: str) -> bool:
         username = username.strip().lower()
         if username not in self.users: