Fix race condition in the telemetry daemon payload processing logic

[ofek]

#274 changed the name of temporary files used for atomic writes so the filter to ignore them no longer worked:

2026-05-14 01:45:50,255 | ERROR | Failed to set up client: .trace
Traceback (most recent call last):
  File "C:\Users\ofek\Desktop\code\datadog-agent-dev\src\dda\telemetry\daemon\__main__.py", line 89, in process_changes
    client = get_client(client_id, **kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\ofek\Desktop\code\datadog-agent-dev\src\dda\telemetry\daemon\__main__.py", line 45, in get_client
    raise ValueError(message)
ValueError: Unknown client ID: .trace

The watcher should never have had knowledge of naming schemes however so now what gets watched is explicit.

The change in the name of temporary files is unnecessary but after thinking about it this is better.