one section per concern, each announced and confirmed before it acts

Three sections where there were two, and none of them touches the machine until
you say so:

  2. System update      upgrades what is already installed
  3. Core utils         what the distribution provides
  4. Command-line tools lazydocker, lazygit, starship, fastfetch

The split matters because these are different kinds of change and deserve
separate answers. System update is the only step in the whole script that moves
versions of software already on the machine; core utils only ever adds what is
absent; and the four tools are upstream binaries the distribution does not ship
at all. Previously the update and the core packages were one step and the tools
were tacked onto the end of it, so agreeing to "essentials" meant agreeing to all
three at once.

Every section now prints what it will install and what it is leaving alone, then
asks. Enter means yes — unlike the machine-role question, which has no default,
because these are "do the thing you already asked for" and making twenty of them
require a deliberate keystroke would train people to hold the y key down.
ASSUME_YES=1 answers all of them for an unattended run, and EOF fails with that
named rather than spinning.

Refusing is recorded rather than glossed: LAST_SKIPPED feeds the summary, so a
declined section reads "Core utils: SKIPPED by request — cowsay neofetch" instead
of quietly reporting nothing installed.

Nothing to install means no prompt at all — there is nothing to agree to.

announce_plan takes the array NAMES rather than their contents, because once a
list has been through word splitting an empty one cannot be told from a missing
one.

Verified all three paths: accept, refuse, and nothing-to-do.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

scripts/setup/machine-setup/lib/tools.sh

@@ -109,6 +109,7 @@ tools_install() {
 
   local tool
   local -a missing=() present=()
+  LAST_SKIPPED=()
   for tool in "$@"; do
     if tool_is_installed "$tool"; then present+=("$tool"); else missing+=("$tool"); fi
   done
@@ -116,15 +117,8 @@ tools_install() {
   LAST_INSTALLED=("${missing[@]}")
   LAST_KEPT=("${present[@]}")
 
-  info "$label — installs what is missing, keeps what you already have"
-  ((${#present[@]})) && echo "     already here: ${present[*]}"
+  announce_plan "$label" present missing || return 0
 
-  if ((${#missing[@]} == 0)); then
-    echo "     to install:   nothing, all present"
-    return 0
-  fi
-
-  echo "     to install:   ${missing[*]}"
   for tool in "${missing[@]}"; do
     info "     installing ${tool}..."
     "tool_install_${tool}"