feat: close #54 V2 install safety, #33 rofi scrollbar, #43 MOTD tip

#54: permanent checks.installer-safety; test-install-safety harness with
offline compose-fail, LUKS-signature disk warn, and HM-hint FORCE paths.
#33: enable themed rofi scrollbars (generated + all whole-swap .rasi).
#43: MOTD + first-boot tip for System › Firmware (V3 LVFS stays hw-queue).

V2: compose-fail/disk-warn/hm-hint logs green offline; theme-shot
boreal+summer-night menus OK. V0 flake/installer-safety.

pkgs/nomarchy-install/nomarchy-install.sh

@@ -454,8 +454,19 @@ PYJSON
 # The flake.lock: composed offline — nomarchy is path-locked to the very
 # source the ISO carries (original stays the forge URL, so a later
 # `nix flake update` on the installed machine re-resolves normally).
-if ! python3 "$SHARE/compose-lock.py" "$SHARE/flake.lock" "$FLAKE_DIR/flake.lock" \
+# NOMARCHY_TEST_FORCE_COMPOSE_FAIL=1 — unattended harness only (#54 V2):
+# pretends compose-lock failed so the offline fail-closed arm is exercised
+# without poisoning the ISO store.
+compose_ok=0
+if [[ "${NOMARCHY_TEST_FORCE_COMPOSE_FAIL:-}" == 1 ]]; then
+    compose_ok=1
+elif python3 "$SHARE/compose-lock.py" "$SHARE/flake.lock" "$FLAKE_DIR/flake.lock" \
         "$NOMARCHY_LOCKED_JSON" "$NOMARCHY_ORIGINAL_JSON"; then
+    compose_ok=0
+else
+    compose_ok=1
+fi
+if (( compose_ok != 0 )); then
     if [[ "$OFFLINE" == true ]]; then
         fail "Offline lock composition failed and there is no network to fall back to — cannot finish an offline install."
     fi
@@ -584,7 +595,19 @@ sleep 2
 runuser -u "$USERNAME" -- bash -lc \
     "USER=$USERNAME HOME=/home/$USERNAME NIX_REMOTE=daemon HOME_MANAGER_BACKUP_EXT=bak \$out/activate"
 EOF
-if nixos-enter --root /mnt -- bash /root/nomarchy-hm-activate.sh; then
+# NOMARCHY_TEST_FORCE_HM_FAIL=1 — unattended harness only (#54 V2): take
+# the failure arm so the durable recovery hint is exercised without a
+# real activation breakage.
+hm_activate_ok=0
+if [[ "${NOMARCHY_TEST_FORCE_HM_FAIL:-}" == 1 ]]; then
+    hm_activate_ok=1
+    warn "NOMARCHY_TEST_FORCE_HM_FAIL=1 — skipping real pre-activate (test harness)"
+elif nixos-enter --root /mnt -- bash /root/nomarchy-hm-activate.sh; then
+    hm_activate_ok=0
+else
+    hm_activate_ok=1
+fi
+if (( hm_activate_ok == 0 )); then
     success "Desktop pre-activated — first boot is fully themed"
 else
     warn "Desktop pre-activation failed (see /var/log/nomarchy-hm-preactivate.log"