[AlexAndBear]

Description

• Listen for Escape on the document while an active modal is open, so body focus after backdrop clicks or re-renders still closes it.
• Keep the focus trap active only for the topmost modal.
• Add regression coverage for Escape after focus leaves the dialog, inactive modals, and loading state.

Related Issue

• Fixes Escape does not close modals after focus leaves dialog #3804

How Has This Been Tested?

• test environment: local Vitest happy-dom unit test run
• test case 1: pnpm exec vitest --config ./tests/unit/config/vitest.config.ts --run --dir packages/design-system/src/components/OcModal
• test case 2: pnpm exec prettier packages/design-system/src/components/OcModal/OcModal.vue packages/design-system/src/components/OcModal/OcModal.spec.ts --config packages/prettier-config/index.js --check
• test case 3: pnpm exec eslint packages/design-system/src/components/OcModal/OcModal.vue packages/design-system/src/components/OcModal/OcModal.spec.ts --color passes with existing vue/require-default-prop warnings

Types of changes

• Bugfix
• Enhancement (a change that doesn't break existing code or deployments)
• Breaking change (a modification affects current functionality)
• Technical debt (addressing code that needs refactoring or improvements)
• Tests (adding or improving tests)
• Documentation (updates or additions to documentation)
• Maintenance (like dependency updates or tooling adjustments)