Get with File on P-ION: connect and transfer the way Ontrol's Niagara driver does

A real P-ION (fw 1.32) restarted on every Sox file get. Ontrol's Niagara 4
driver gets app.sab from the same device, so its settings are copied:
- DASP hello asks for 256-byte packets (idealMax/absMax), so file chunks
  are 238 bytes
- the message-length header (0x81) goes to Orion only, decided once the
  platform id is read
- the app is saved on the device before app.sab is read, the save resent
  every 5 s rather than 1 s (a P-ION save takes 2-3+ s)
- the file open is resent every 15 s; DASP gains a per-packet resend
  interval for this

Tested on a P-ION at 192.168.1.252: save 3.2 s, app.sab + kits.scode +
app.sax in 15.8 s, no resends, device stayed up. The unsaved-changes
question became a notice, since the app is now always saved first.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

device_session.py

@@ -10,6 +10,7 @@ import xml.etree.ElementTree as ET
 
 import app_state
 import schema
+import sox
 from sox import SoxClient, SoxComponent, TREE, CONFIG, RUNTIME, LINKS, ALL
 
 
@@ -43,7 +44,8 @@ class DeviceSession:
 
     def connect(self, host, port, user, password):
         """DASP connect → read schema → load root. Called from background thread."""
-        self.sox_client = SoxClient(host, int(port), user, password)
+        self.sox_client = SoxClient(host, int(port), user, password,
+                                    ideal_max=sox.IDEAL_MAX, abs_max=sox.ABS_MAX)
         self.sox_client.on_event = self._on_sox_event
         self.sox_client.checksum_resolver = schema.resolve_truncated_checksum
         self.sox_client.connect()