plan(SP22): Task 5 — apply Task 4 fixes (4xx terminal, RuntimeError) to list_claims and parse_837

docs/superpowers/plans/2026-06-21-cyclone-pipeline-agent.md

@@ -980,7 +980,8 @@ Add the methods to the `CycloneClient` class (below `scheduler_status`):
         params: dict[str, str] = {"limit": str(limit)}
         if since:
             params["since"] = since
-        assert self._http is not None
+        if self._http is None:
+            raise RuntimeError("use `async with CycloneClient(...)`")
         last_exc: Exception | None = None
         for attempt in range(MAX_RETRIES):
             try:
@@ -992,10 +993,15 @@ Add the methods to the `CycloneClient` class (below `scheduler_status`):
                     ClaimSummary.model_validate(c)
                     for c in _extract_items(resp.json())
                 ]
-            except (httpx.HTTPStatusError, httpx.RequestError) as e:
+            except httpx.HTTPStatusError as e:
+                # 4xx is terminal — surface immediately, do not retry
+                if e.response is not None and e.response.status_code < 500:
+                    raise
                 last_exc = e
-                if attempt < MAX_RETRIES - 1:
-                    await asyncio.sleep(BACKOFF_S[attempt])
+            except httpx.RequestError as e:
+                last_exc = e
+            if attempt < MAX_RETRIES - 1:
+                await asyncio.sleep(BACKOFF_S[attempt])
         assert last_exc is not None
         raise last_exc
 
@@ -1003,11 +1009,13 @@ Add the methods to the `CycloneClient` class (below `scheduler_status`):
         self, file_path, payer: str = "co_medicaid"
     ) -> ParseSummary:
         """POST the .edi/.txt file to cyclone's parse endpoint.
-        Returns a typed summary.
+        Returns a typed summary. POSTs are not retried on transport
+        failures (caller is responsible for dedup).
         """
         from pathlib import Path  # local import keeps the top of the file lean
         path = Path(file_path)
-        assert self._http is not None
+        if self._http is None:
+            raise RuntimeError("use `async with CycloneClient(...)`")
         with path.open("rb") as f:
             resp = await self._http.post(
                 "/api/parse-837",