[ZSH] Set history size before anything interruptible

An aborted startup kept /etc/zshrc's SAVEHIST=1000 and truncated
~/.zsh_history on exit.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

zsh/.zshrc

@@ -1,3 +1,9 @@
+# First, so an interrupted startup (Ctrl-C) doesn't keep /etc/zshrc's
+# SAVEHIST=1000 and truncate the history file on exit
+HISTSIZE=100000
+SAVEHIST=100000
+setopt EXTENDED_HISTORY
+
 source "${ZDOTDIR:-$HOME}/.zsh/lib/startup.zsh"
 [[ -d ${ZDOTDIR:-$HOME}/.cache/zsh ]] || mkdir -p ${ZDOTDIR:-$HOME}/.cache/zsh