Log each install and update, and keep only the recent logs

Each run's output now goes to ~/.local/state/coredesktop/logs/, so what
failed can be read after the terminal is gone. In a terminal, update runs
itself under script(1), so everything it runs still sees a terminal, then
strips color codes and progress redraws from the log; otherwise it uses
tee. install.sh, usually piped into bash, uses tee, and runs configure
straight on the terminal, outside the log. Both name the log when
something fails. 95-cleanup.sh keeps the newest 10 update logs and 3
install logs.

The sudo keepalive loops no longer share the logged output, so their
sleep can't hold the log open after the run ends.

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

install.sh

@@ -21,6 +21,14 @@ clear
 print_logo
 cd
 
+# Log the install to ~/.local/state/coredesktop/logs (update deletes old ones).
+# It's usually piped into bash, so it can't run itself again under script(1)
+# the way update does; send its output through tee instead.
+if mkdir -p -m 700 "$HOME/.local/state/coredesktop/logs"; then
+  INSTALL_LOG="$HOME/.local/state/coredesktop/logs/install-$(date +%Y-%m-%d-%H%M%S).log"
+  exec > >(tee -a "$INSTALL_LOG") 2>&1
+fi
+
 # Exit on any error
 set -e
 
@@ -51,9 +59,16 @@ if ! sudo -v; then
   echo "archinstall, make the user a superuser): https://wiki.archlinux.org/title/Sudo"
   exit 1
 fi
-while kill -0 $$ 2> /dev/null; do sudo -n -v; sleep 60; done 2> /dev/null &
+while kill -0 $$ 2> /dev/null; do sudo -n -v; sleep 60; done > /dev/null 2>&1 &
 SUDO_KEEPALIVE_PID=$!
-trap 'kill "$SUDO_KEEPALIVE_PID" 2> /dev/null' EXIT
+on_exit() {
+  local status=$?
+  kill "$SUDO_KEEPALIVE_PID" 2> /dev/null
+  if (( status != 0 )) && [ -n "$INSTALL_LOG" ]; then
+    echo "The install stopped with an error. The full output is in $INSTALL_LOG"
+  fi
+}
+trap on_exit EXIT
 
 # Ensure git is available before attempting to clone anything
 if ! command -v git &> /dev/null; then
@@ -283,7 +298,9 @@ if ~/.local/bin/configure --list | grep -q '^to do'; then
   echo "$CONFIGURE_HINT"
   if { : < /dev/tty; } 2> /dev/null && read -rp "Run configure now? [Y/n] " answer < /dev/tty \
       && [[ "$answer" != [nN]* ]]; then
-    ~/.local/bin/configure < /dev/tty || true
+    # Straight to the terminal, outside the log: sign-ins need a terminal, and
+    # their codes and links don't belong in a log
+    ~/.local/bin/configure < /dev/tty > /dev/tty 2>&1 || true
   else
     echo "To do it later, run: configure"
   fi