Localization: run the AI translation tooling unit tests in CI

The pure-Ruby unit suites (TranslationValidator, Glossary, AnthropicBatch,
AITranslator) weren't executed by any pipeline step — the "Unit Tests" jobs are
the Xcode/XCTest suites, and rubocop (via Danger) only lints them. Add a
lightweight Buildkite step that runs each fastlane/lanes/*_test.rb with plain
ruby (stdlib minitest — no Xcode, no app build, no bundle).

Runs unconditionally rather than behind should-skip-job.sh --job-type validation,
which skips on tooling-only changes — i.e. exactly the PRs that touch these files.

Author: jkmassel

.buildkite/commands/test-localization-tooling.sh

@@ -0,0 +1,22 @@
+#!/bin/bash -eu
+
+# Runs the localization tooling's pure-Ruby unit suites (stdlib minitest — no Xcode, no app build, no bundle).
+# Intentionally always runs (no should-skip-job guard): these guard the fastlane localization helpers, and the
+# `validation` skip rule skips on tooling-only changes — exactly when these tests matter most.
+
+echo "--- :test_tube: Localization tooling unit tests"
+
+shopt -s nullglob
+tests=(fastlane/lanes/*_test.rb)
+if [[ ${#tests[@]} -eq 0 ]]; then
+  echo "No *_test.rb files found under fastlane/lanes/."
+  exit 0
+fi
+
+status=0
+for test in "${tests[@]}"; do
+  echo "+++ :ruby: ${test}"
+  ruby "${test}" || status=1
+done
+
+exit "${status}"

.buildkite/pipeline.yml

@@ -163,6 +163,13 @@ steps:
           - github_commit_status:
               context: "Verify String Catalog Coverage"
 
+      - label: ":test_tube: Localization Tooling Unit Tests"
+        command: .buildkite/commands/test-localization-tooling.sh
+        plugins: [$CI_TOOLKIT_PLUGIN]
+        notify:
+          - github_commit_status:
+              context: "Localization Tooling Unit Tests"
+
   #################
   # Claude Build Analysis - dynamically uploaded so Build result conditions evaluate at runtime after the wait
   #################