test(layout): add empty fallback coverage

[sanzzzz-g]

Description

Fixes #4243

Added isolated empty fallback and edge-case test coverage for app/layout.tsx.

Coverage added

• verifies layout renders safely with null children
• verifies layout renders safely with undefined children
• ensures fallback main container remains stable during empty states
• validates accessibility skip-link rendering
• confirms metadata and viewport defaults remain intact
• ensures no hydration/runtime failures occur during empty rendering

Pillar

• 🛠️ Other (Bug fix, refactoring, docs)

Visual Preview

N/A (test-only changes)

Checklist before requesting a review:

• I have read the CONTRIBUTING.md file.
• I have tested these changes locally (localhost:3000/api/streak?user=YOUR_USERNAME).
• I have run npm run format and npm run lint locally and resolved all errors (CI will fail otherwise).
• My commits follow the Conventional Commits format (e.g., feat(themes): ..., fix(calculate): ...).
• I have started the repo.
• I have made sure that I have only one commit to merge in this PR.
• The SVG output matches the CommitPulse "premium quality" aesthetic standard (no raw elements, smooth animations, correct fonts).

[github-actions]

📦 Next.js Bundle Size Report (Gzipped Sizes)

Asset	PR Size	Base Size	Difference	Status
static/chunks/2373-[hash].js	41.60 KB	41.88 KB	-0.29 KB (-0.68%)	🟢 Improvement
static/chunks/9453-[hash].js	93.37 KB	93.33 KB	+0.04 KB (+0.04%)	🔴 Regression

📊 Summary of Totals

Category	PR Size	Base Size	Difference
Total JS	3708.66 KB	3710.63 KB	-1.97 KB (-0.05%)
Total CSS	290.64 KB	290.64 KB	0 B

[Aamod-Dev]

GSSoC 2025 Mentor Review — @Aamod007

Labels: level:beginner, type:testing, mentor:Aamod007

Difficulty (beginner): Single test file testing React render resilience with null/undefined children.

Type (testing): Adds empty fallback coverage for root layout. Fixes #4243.

LGTM — good resilience testing for edge cases.

[github-actions]

🚨 Hey @sanzzzz-g, the CI Pipeline is failing on this PR and it has been marked as status:blocked.

Please fix the issues before this can be reviewed. Here's how:

1. Run checks locally before pushing:

npm run format:check   # Check Prettier formatting
npm run lint           # Run ESLint
npm run typecheck      # TypeScript type check
npm run test           # Run unit tests (Vitest)
npm run build          # Verify production build passes

2. Auto-fix common issues:

npm run format         # Auto-fix formatting with Prettier
npm run lint -- --fix  # Auto-fix lint errors where possible

3. Check the full failure log here:
👉 View CI Run

Once you push a fix and the CI passes, the status:blocked label will be removed automatically. 💪