zsh: strip control characters from window title (#10341)

## Summary
- Fix literal \n appearing in window titles when running commands in zsh

## Description
The zsh shell integration was using ${(V)1} parameter expansion to set
the window title. The (V) flag converts control characters to their
visible escape sequence representations, causing commands ending with a
newline to display as command\n in the title bar.

Changed to use ${1//[[:cntrl:]]} which strips control characters
entirely, matching the behavior of the bash integration.

<img width="231" height="47" alt="image"
src="https://github.com/user-attachments/assets/356c77a1-32da-47b0-bf86-29735cc67e90"
/>

## Test

  - Open Ghostty with zsh shell integration enabled
  - Run a command (e.g., cargo install trunk)

  ---
AI Disclosure: This PR was written primarily by Claude Code. (Opus 4.5)

src/shell-integration/zsh/ghostty-integration

@@ -201,11 +201,11 @@ _ghostty_deferred_init() {
     _ghostty_report_pwd
 
     if [[ "$GHOSTTY_SHELL_FEATURES" == *"title"* ]]; then
-      # Enable terminal title changes.
+      # Enable terminal title changes, formatted for user-friendly display.
       functions[_ghostty_precmd]+="
           builtin print -rnu $_ghostty_fd \$'\\e]2;'\"\${(%):-%(4~|…/%3~|%~)}\"\$'\\a'"
       functions[_ghostty_preexec]+="
-          builtin print -rnu $_ghostty_fd \$'\\e]2;'\"\${(V)1}\"\$'\\a'"
+          builtin print -rnu $_ghostty_fd \$'\\e]2;'\"\${1//[[:cntrl:]]}\"\$'\\a'"
     fi
 
     if [[ "$GHOSTTY_SHELL_FEATURES" == *"cursor"* ]]; then