Add fzf-tab plugin (navigable Tab completion menu)

Kaiser's existing .zshrc had fzf-tab added to the plugins list —
it gives a navigable Tab completion menu with descriptions for each
match. Adding to the canonical plugin list so kaiser doesn't lose
functionality when the repo version overwrites the box-specific
one. Strictly additive: doesn't affect miche or other boxes.

Adds:
- fzf-tab to dot_zshrc.tmpl plugins array
- install_zsh_plugin Aloxaf/fzf-tab to run_once_20

dot_zshrc.tmpl

@@ -22,6 +22,7 @@ plugins=(
     rust
     rsync
     command-not-found
+    fzf-tab                       # navigable Tab completion menu
     zsh-syntax-highlighting       # fish-style live colors — MUST be near last
     zsh-history-substring-search  # fish-style Up/Down history search
     zsh-autosuggestions           # fish-style ghost completions — MUST be last

run_once_20-install-user-packages.sh.tmpl

@@ -6,7 +6,7 @@
 #  starship, lazygit, yt-dlp, etc.)
 #
 #  Also: install oh-my-zsh, zsh-autosuggestions, zsh-syntax-highlighting,
-#  zsh-history-substring-search.
+#  zsh-history-substring-search, fzf-tab.
 #
 #  Runs as the unprivileged user, but uses sudo for system packages.
 # =============================================================================
@@ -141,6 +141,7 @@ install_zsh_plugin() {
 install_zsh_plugin zsh-users/zsh-autosuggestions        "$ZSH_CUSTOM/plugins/zsh-autosuggestions"
 install_zsh_plugin zsh-users/zsh-syntax-highlighting    "$ZSH_CUSTOM/plugins/zsh-syntax-highlighting"
 install_zsh_plugin zsh-users/zsh-history-substring-search "$ZSH_CUSTOM/plugins/zsh-history-substring-search"
+install_zsh_plugin Aloxaf/fzf-tab                       "$ZSH_CUSTOM/plugins/fzf-tab"
 
 # --------------------------- TPM (tmux plugin manager) ---------------------
 if [[ ! -d "$USER_HOME/.tmux/plugins/tpm" ]]; then