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/src/pty/session.dart

@@ -370,7 +370,7 @@ class _ReaderArgs {
 /// each chunk back to the main isolate as a `Uint8List`. Exits on
 /// EOF, close, or error.
 void _readerEntrypoint(_ReaderArgs args) {
-  const chunk = 4096;
+  const chunk = 65536;
   final buf = pkg_ffi.calloc<ffi.Uint8>(chunk);
   try {
     while (true) {