tools/mpremote: Fix disconnect handling on Windows and Linux.

Changes in this commit:
- Handle SerialException on Windows when device disconnects.
- Print clean 'device disconnected' message instead of stack trace.
- Fix terminal formatting issues on Linux after disconnect.
- Return disconnected state after console cleanup to avoid terminal issues.

This ensures proper disconnect messages on both platforms without showing
confusing error traces to users.

Signed-off-by: Andrew Leech <andrew.leech@planetinnovation.com.au>

tools/mpremote/mpremote/main.py

@@ -620,7 +620,11 @@ def main():
         # If no commands were "actions" then implicitly finish with the REPL
         # using default args.
         if state.run_repl_on_completion():
-            do_repl(state, argparse_repl().parse_args([]))
+            disconnected = do_repl(state, argparse_repl().parse_args([]))
+
+            # Handle disconnection message
+            if disconnected:
+                print("\ndevice disconnected")
 
         return 0
     except CommandError as e:

tools/mpremote/mpremote/repl.py

@@ -7,6 +7,7 @@ def do_repl_main_loop(
     state, console_in, console_out_write, *, escape_non_printable, code_to_inject, file_to_inject
 ):
     while True:
+        try:
             console_in.waitchar(state.transport.serial)
             c = console_in.readchar()
             if c:
@@ -31,13 +32,7 @@ def do_repl_main_loop(
                 else:
                     state.transport.serial.write(c)
 
-        try:
             n = state.transport.serial.inWaiting()
-        except OSError as er:
-            if er.args[0] == 5:  # IO error, device disappeared
-                print("device disconnected")
-                break
-
             if n > 0:
                 dev_data_in = state.transport.serial.read(n)
                 if dev_data_in is not None:
@@ -53,6 +48,13 @@ def do_repl_main_loop(
                         console_data_out = dev_data_in
                     console_out_write(console_data_out)
 
+        except OSError as er:
+            if _is_disconnect_exception(er):
+                return True
+            else:
+                raise
+    return False
+
 
 def do_repl(state, args):
     state.ensure_friendly_repl()
@@ -86,7 +88,7 @@ def do_repl(state, args):
             capture_file.flush()
 
     try:
-        do_repl_main_loop(
+        return do_repl_main_loop(
             state,
             console,
             console_out_write,
@@ -98,3 +100,22 @@ def do_repl(state, args):
         console.exit()
         if capture_file is not None:
             capture_file.close()
+
+
+def _is_disconnect_exception(exception):
+    """
+    Check if an exception indicates device disconnect.
+
+    Returns True if the exception indicates the device has disconnected,
+    False otherwise.
+    """
+    if isinstance(exception, OSError):
+        if hasattr(exception, 'args') and len(exception.args) > 0:
+            # IO error, device disappeared
+            if exception.args[0] == 5:
+                return True
+        # Check for common disconnect messages in the exception string
+        exception_str = str(exception)
+        disconnect_indicators = ["Write timeout", "Device disconnected", "ClearCommError failed"]
+        return any(indicator in exception_str for indicator in disconnect_indicators)
+    return False