fix: Char namedtuple save/restore — use blink not width, construct new Char objects

pyte.screens.Char is a namedtuple (immutable), so fields can't be
mutated directly. Also 'width' doesn't exist — the correct field is
'blink'. Now creates new Char(...) objects for buffer restoration.
Fixes server switching being completely broken (AttributeError on save).

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

gui/widgets/terminal_widget.py

@@ -364,6 +364,7 @@ class TerminalWidget(tk.Frame):
     def get_current_buffer(self) -> bytes:
         """Export full pyte screen state as serialized data for session pool."""
         import pickle
+        from pyte.screens import Char
 
         screen_state = {
             'buffer': {},
@@ -380,11 +381,12 @@ class TerminalWidget(tk.Frame):
             line_dict = {}
             for x in range(self._screen.columns):
                 c = self._screen.buffer[y][x]
+                # Char is a namedtuple — store all fields
                 line_dict[x] = {
                     'data': c.data, 'fg': c.fg, 'bg': c.bg,
                     'bold': c.bold, 'italics': c.italics,
                     'underscore': c.underscore, 'reverse': c.reverse,
-                    'strikethrough': c.strikethrough, 'width': c.width,
+                    'strikethrough': c.strikethrough, 'blink': c.blink,
                 }
             screen_state['buffer'][y] = line_dict
 
@@ -393,6 +395,7 @@ class TerminalWidget(tk.Frame):
     def restore_buffer(self, buffer_data: bytes):
         """Restore full pyte screen state from serialized data."""
         import pickle
+        from pyte.screens import Char
 
         try:
             state = pickle.loads(buffer_data)
@@ -403,22 +406,20 @@ class TerminalWidget(tk.Frame):
             self._screen.reset()
             self._screen.resize(rows, cols)
 
+            # Char is a namedtuple — must replace entire objects
             for y, line_dict in state['buffer'].items():
                 if y >= self._screen.lines:
                     continue
                 for x, cd in line_dict.items():
                     if x >= self._screen.columns:
                         continue
-                    ch = self._screen.buffer[y][x]
-                    ch.data = cd['data']
-                    ch.fg = cd['fg']
-                    ch.bg = cd['bg']
-                    ch.bold = cd['bold']
-                    ch.italics = cd['italics']
-                    ch.underscore = cd['underscore']
-                    ch.reverse = cd['reverse']
-                    ch.strikethrough = cd['strikethrough']
-                    ch.width = cd['width']
+                    self._screen.buffer[y][x] = Char(
+                        data=cd['data'], fg=cd['fg'], bg=cd['bg'],
+                        bold=cd['bold'], italics=cd['italics'],
+                        underscore=cd['underscore'], reverse=cd['reverse'],
+                        strikethrough=cd['strikethrough'],
+                        blink=cd.get('blink', False),
+                    )
 
             self._screen.cursor.x = state.get('cursor_x', 0)
             self._screen.cursor.y = state.get('cursor_y', 0)