Zsh: Adopt tabtab completion block into managed zshrc

JS CLIs that bundle tabtab (today: td, the Todoist CLI) append a
completion-sourcing block to ~/.zshrc, which chezmoi then wants to
strip on every apply — an endless tug-of-war.

Tabtab cannot be disabled globally, but its installer is idempotent:
it skips the append when its source line is already present. Owning
the exact block in dot_zshrc ends the churn, and the [[ -f ]] guard
makes it a no-op on machines without tabtab completions.

Author: jdevera

home/dot_zshrc

@@ -9,3 +9,7 @@ dot::bootstrap
 # -----------------------------------------------------------------------------
 # This is where all sort of random commands will append their stuff
 # -----------------------------------------------------------------------------
+
+# tabtab source for packages
+# uninstall by removing these lines
+[[ -f ~/.config/tabtab/zsh/__tabtab.zsh ]] && . ~/.config/tabtab/zsh/__tabtab.zsh || true