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>

assets/clide.tmux.conf

@@ -0,0 +1,35 @@
+# clide tmux.conf — loaded via tmux -f for every Claude pane session.
+# Tuned for embedding inside xterm.dart; no status bar, large
+# scrollback, mouse-scroll passthrough, zero escape delay.
+
+# No status bar — clide renders its own pane chrome.
+set -g status off
+
+# 50k lines of scrollback (tmux default is 2000).
+set -g history-limit 50000
+
+# Zero escape delay — xterm.dart delivers escape sequences
+# atomically, so the 500ms default just adds latency.
+set -sg escape-time 0
+
+# Mouse on — scroll wheel events reach tmux's copy-mode so the
+# user can scroll back through Claude output.
+set -g mouse on
+
+# 256color + true-color passthrough.
+set -g default-terminal "xterm-256color"
+set -ga terminal-overrides ",xterm-256color:Tc"
+
+# Don't ring the bell visually or audibly — clide owns notifications.
+set -g visual-bell off
+set -g bell-action none
+
+# Keep the session alive when the shell exits — clide manages
+# lifecycle via pane.close, not tmux session destruction.
+set -g remain-on-exit off
+
+# Allow alt-screen passthrough for full-screen programs.
+set -g alternate-screen on
+
+# Focus events let the terminal's focus tracking work through tmux.
+set -g focus-events on