feat: prepare ARR for controlled public deployment

arr_processing/errors.py

@@ -0,0 +1,27 @@
+"""Stable, non-sensitive processing orchestration errors."""
+
+from __future__ import annotations
+
+
+class ProcessingError(RuntimeError):
+    def __init__(self, code: str, safe_message: str, *, retryable: bool = False) -> None:
+        super().__init__(safe_message)
+        self.code = code
+        self.safe_message = safe_message
+        self.retryable = retryable
+
+
+class ProcessingTransportError(RuntimeError):
+    """Normalized remote transport failure; raw response bodies are never retained."""
+
+    def __init__(
+        self,
+        code: str,
+        *,
+        retryable: bool,
+        active_run_conflict: bool = False,
+    ) -> None:
+        super().__init__(code)
+        self.code = code
+        self.retryable = retryable
+        self.active_run_conflict = active_run_conflict