test(template): add type compiler validation tests

[pari7maheshwari]

Description

Fixes #2872

Added app/template.type-compiler.test.tsx to provide isolated type compiler validation and schema constraint stability coverage for app/template.tsx.

Implemented 5 tests covering:

• Type enforcement for the children prop using expectTypeOf
• Validation that invalid prop parameters are blocked during static type checking
• Optional/valid ReactNode compatibility checks
• Runtime rendering validation for valid children
• Stability verification for null children without runtime crashes

Verified the new test file passes with:
npx vitest run app/template.type-compiler.test.tsx

Pillar

• 🎨 Pillar 1 — New Theme Design
• 📐 Pillar 2 — Geometric SVG Improvement
• 🕐 Pillar 3 — Timezone Logic Optimization
• 🛠️ Other (Bug fix, refactoring, docs)

Visual Preview

N/A (test-only change)

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 updated README.md if I added a new theme or URL parameter.
• 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).
• (Recommended) I joined the CommitPulse Discord community for contributor discussions, mentorship, and faster PR support.

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