feat(scripts): implement report-status.sh with bats and cucumber tests

POST build status to Gitea REST API. Supports pending, success, failure,
error states. Cross-repo reporting via optional root_commit and root_repo
parameters. Includes mock Gitea API server shared between bats unit tests
and cucumber acceptance tests.

cucumber.js

@@ -0,0 +1,8 @@
+module.exports = {
+  default: {
+    paths: ['tests/features/*.feature'],
+    require: ['tests/features/step_definitions/*.steps.js'],
+    format: ['progress-bar'],
+    tags: 'not @wip',
+  },
+};