test: add typed route regression coverage

[tatakaisun]

Summary

Add regression coverage for typed i18n routes with useRoute().params and RouteLocationRaw props.

Why

Issue #3954 reports typed route regressions after the vue-router v5 update.

Changes

• Add an issue-specific typedPages + i18n fixture
• Add type-level assertions for route params and RouteLocationRaw

Testing

• pnpm dev:prepare
• pnpm exec vitest run specs/experimental/typed_pages.spec.ts
• pnpm exec vitest run specs/issues/3954.spec.ts
• git diff --check

Known Issues

The minimal reproduction passes on current main, so this PR adds coverage only and does not change production types.

Summary by CodeRabbit

• Tests
  • Added regression test suite for issue #3954 validating TypeScript type diagnostics with internationalization and typed route declarations. The tests ensure route parameters maintain correct type narrowing when using typed pages with localization, and prevent unexpected expansion of route location unions when used in component props.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 16031d5e-8f6c-4ebb-b478-15bca9648ad1

📥 Commits

Reviewing files that changed from the base of the PR and between 8cc7ca8 and 1bf99a5.

📒 Files selected for processing (6)

• specs/fixtures/issues/3954/app.vue
• specs/fixtures/issues/3954/components/MyLink.vue
• specs/fixtures/issues/3954/nuxt.config.ts
• specs/fixtures/issues/3954/pages/index.vue
• specs/fixtures/issues/3954/pages/widget/[widgetId].vue
• specs/issues/3954.spec.ts

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Walkthrough

This PR adds a regression test fixture for issue #3954, which validates TypeScript type narrowing in Nuxt routes when using the i18n module with typed pages. The fixture includes a Nuxt application configured with i18n (supporting en and fr locales) and typed pages enabled, a reusable MyLink component that accepts RouteLocationRaw, index and dynamic widget pages, and a comprehensive TypeScript diagnostics test that verifies route parameter types remain narrowed and that RouteLocationRaw unions do not expand unexpectedly in i18n route definitions.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'test: add typed route regression coverage' accurately reflects the main purpose of the PR, which adds regression test coverage for typed i18n routes with focused test cases validating type diagnostics.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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