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>

main.py

@@ -619,9 +619,9 @@ _APP_ACTIONS = ["save", "hibernate", "quit", "restart", "reboot"]
 def do_get_with_file():
     """App > Get with File: backs the device's app up to a zip in <Sedona home>/store/apps.
 
-    The zip carries the device's app.sab, so changes not yet saved on the device are
-    offered a save first. The transfer runs off the main thread behind a small progress
-    window.
+    The app is saved on the device before its app.sab is read, as Ontrol's Niagara
+    driver does, so unsaved changes are announced first and the backup can be called
+    off. The transfer runs off the main thread behind a small progress window.
     """
     ds = app_state.device_session
     if not app_state.live_mode or ds is None or not ds.is_connected:
@@ -631,21 +631,11 @@ def do_get_with_file():
         messagebox.showerror("Get with File", "The Sedona home folder is not set (Preferences).")
         return
 
-    if app_state.is_dirty:
-        answer = messagebox.askyesnocancel(
+    if app_state.is_dirty and not messagebox.askokcancel(
             "Unsaved Changes",
             "The app has changes that are not saved on the device yet." + NL + NL +
-            "Save the app on the device before getting it?" + NL +
-            "(No gets the app as it was last saved.)",
-        )
-        if answer is None:
-            return
-        if answer and not _invoke_app_action("save"):
-            messagebox.showerror(
-                "Get with File",
-                "The device did not save the app, so nothing was fetched. "
-                "The status bar says why.")
-            return
+            "Get with File saves the app on the device first, so they will be saved."):
+        return
 
     path = _ask_backup_path(ds)
     if not path:
@@ -683,6 +673,7 @@ def do_get_with_file():
             app_state.set_status(f"Get with File failed: {error}", warn=True)
             messagebox.showerror("Get with File", f"The backup failed:{NL}{NL}{error}")
             return
+        app_state.mark_clean()          # the app was saved on the device first
         _report_backup(result)
 
     def work():