fix: stabilize external-db deployment and updates

scripts/test-install-fixture.sh

@@ -28,6 +28,7 @@ mode_of() {
   sed -n '/^database_host()/,/^}/p' "$ROOT/deploy/install.sh"
   sed -n '/^database_port()/,/^}/p' "$ROOT/deploy/install.sh"
   sed -n '/^database_name()/,/^}/p' "$ROOT/deploy/install.sh"
+  sed -n '/^validate_database_configuration()/,/^}/p' "$ROOT/deploy/install.sh"
   sed -n '/^is_semver()/,/^}/p' "$ROOT/deploy/install.sh"
   sed -n '/^write_env_file_preserving_unknown()/,/^}/p' "$ROOT/deploy/install.sh"
   sed -n '/^normalized_host_arch()/,/^}/p' "$ROOT/deploy/install.sh"
@@ -41,13 +42,15 @@ mode_of() {
   sed -n '/^release_asset_url()/,/^}/p' "$ROOT/deploy/install.sh"
   sed -n '/^download_release_asset()/,/^}/p' "$ROOT/deploy/install.sh"
   sed -n '/^install_packages()/,/^}/p' "$ROOT/deploy/install.sh"
-  sed -n '/^mysql_client_bin()/,/^}/p' "$ROOT/deploy/install.sh"
   sed -n '/^preflight_database()/,/^}/p' "$ROOT/deploy/install.sh"
   sed -n '/^secure_release_tree()/,/^}/p' "$ROOT/deploy/install.sh"
   sed -n '/^restore_unit_state()/,/^}/p' "$ROOT/deploy/install.sh"
 } > "$WORK/helpers.sh"
 # shellcheck disable=SC1090,SC1091
 source "$WORK/helpers.sh"
+# Avoid invoking the host's macOS `log` utility while exercising extracted
+# installer helpers.
+log() { printf '%s\n' "$*" >/dev/null; }
 
 export SETUP_WIZARD=true
 preflight_database || fail 'setup wizard database preflight returned a failure status'
@@ -66,10 +69,21 @@ cat > "$WORK/mysql-bin/mysql" <<'SH'
 exit 0
 SH
 chmod 0755 "$WORK/mysql-bin/mysql"
-export KAIDI_MYSQL_CLIENT="$WORK/mysql-bin/mysql"
-[ "$(mysql_client_bin)" = "$WORK/mysql-bin/mysql" ] \
-  || fail 'installer did not honor the explicit MySQL client path'
-unset KAIDI_MYSQL_CLIENT
+# Production-mode validation is intentionally side-effect free: it validates
+# the JDBC shape but never invokes a MySQL client or emits DDL/DML.
+SETUP_WIZARD=false
+DB_URL='jdbc:mysql://127.0.0.1:3306/kaidi_finance?useUnicode=true'
+DB_USERNAME='fixture-user'
+DB_PASSWORD='fixture-password'
+mysql_probe_marker="$WORK/mysql-probe-called"
+cat > "$WORK/mysql-bin/mysql" <<SH
+#!/bin/sh
+printf 'called\n' > "$mysql_probe_marker"
+exit 99
+SH
+chmod 0755 "$WORK/mysql-bin/mysql"
+preflight_database || fail 'side-effect-free database configuration validation returned a failure status'
+[ ! -e "$mysql_probe_marker" ] || fail 'installer invoked a MySQL client during configuration validation'
 
 release_permissions="$WORK/release-permissions"
 mkdir -p "$release_permissions/public" "$release_permissions/ops"