fix: treat DSM 599 as task-not-ready in _poll_task, poll until 60s timeout

DirSize/MD5 return error 599 while the async task is still initialising on
the NAS, not only after the task is gone. Remove the 5-consecutive-599 abort
limit and the debug stderr logging; instead pass on 599 and keep polling
until the existing 60 s timeout fires. Rename the test that checked the old
limit to reflect the new timeout-based behaviour.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/mcp_synology_filestation/tools/filestation.py

@@ -81,26 +81,16 @@ def register_filestation(
             ``(True, status_dict)`` on success, or ``(False, "Error: …")`` on
             DSM error or timeout.
         """
-        import sys as _sys
-
         from mcp_synology_filestation.client import SynologyError as _SynologyError
 
         delay = 0.2
         elapsed = initial_delay
         timeout = 60.0
-        consecutive_599 = 0
-        attempt = 0
-
-        _sys.stderr.write(
-            f"[poll] START {api}/status v{version} taskid={taskid} initial_delay={initial_delay}\n"
-        )
-        _sys.stderr.flush()
 
         if initial_delay > 0:
             await asyncio.sleep(initial_delay)
 
         while True:
-            attempt += 1
             try:
                 status_data = await client.request(
                     api,
@@ -108,25 +98,12 @@ def register_filestation(
                     version=version,
                     params={"taskid": taskid},
                 )
-                consecutive_599 = 0
-                finished = status_data.get("finished")
-                _sys.stderr.write(
-                    f"[poll] #{attempt} elapsed={elapsed:.2f}s finished={finished}"
-                    f" data_keys={list(status_data.keys())}\n"
-                )
-                _sys.stderr.flush()
             except _SynologyError as e:
-                _sys.stderr.write(
-                    f"[poll] #{attempt} elapsed={elapsed:.2f}s"
-                    f" SynologyError code={e.code} msg={e}\n"
-                )
-                _sys.stderr.flush()
                 if e.code == 599:
-                    # 599 can be transient (task just started, not yet available).
-                    # Retry up to 5 times before giving up.
-                    consecutive_599 += 1
-                    if consecutive_599 >= 5:
-                        return False, f"Error: {e}"
+                    # DSM returns 599 while the async task is still initialising
+                    # or running (task-not-yet-available). Treat it the same as
+                    # finished=False and keep polling until the 60 s timeout.
+                    pass
                 else:
                     return False, f"Error: {e}"
             else: