inline terminal emulator, drop xterm.dart dependency

Replace the xterm pub.dev package with owned code under
lib/src/terminal/. Based on xterm.dart v4.0.0 by xuty (MIT).
Quiver LRU replaced with hand-rolled LinkedHashMap cache.
Scrollable removed from TerminalView — scroll events are forwarded
via Listener.onPointerSignal instead. zmodem, debugger, and
suggestion modules stripped as unused.

Also: bundle clide.tmux.conf (no status bar, 50k scrollback,
mouse on, zero escape delay, isolated -L clide socket), bump PTY
read buffer to 64KB, add 2px terminal padding, drop bold
JetBrains Mono registration.

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

lib/widgets/src/clide_pty_view.dart

@@ -2,7 +2,7 @@ import 'package:clide/kernel/src/theme/controller.dart';
 import 'package:clide/kernel/src/theme/tokens.dart';
 import 'package:clide/widgets/src/typography.dart';
 import 'package:flutter/widgets.dart';
-import 'package:xterm/xterm.dart';
+import 'package:clide/src/terminal/terminal.dart';
 
 /// Theme-aware terminal view. Wraps xterm.dart's [TerminalView] with
 /// clide token bindings, JetBrainsMono as the face, and a Semantics
@@ -54,7 +54,7 @@ class ClidePtyView extends StatelessWidget {
             fontFamily: clideMonoFamily,
             fontFamilyFallback: clideMonoFamilyFallback,
           ),
-          padding: EdgeInsets.zero,
+          padding: const EdgeInsets.all(2),
           backgroundOpacity: 1,
           cursorType: TerminalCursorType.block,
         ),