feat: CI build cache

[harlan-zw]

Summary

• Adds buildCache config option for persistent caching of rendered OG images between CI runs
• Cache key includes options hash, component template hash, and module version for automatic invalidation
• Stores cache in node_modules/.cache/nuxt/og-image/ by default

Usage

export default defineNuxtConfig({
  ogImage: {
    buildCache: true
  }
})

Cache Invalidation

The cache automatically invalidates when:

• Options change - Different title, description, or other props
• Template changes - The component file is modified
• Module version changes - You upgrade nuxt-og-image

CI Configuration

- uses: actions/cache@v4
  with:
    path: node_modules/.cache/nuxt/og-image
    key: og-images-${{ hashFiles('**/package-lock.json') }}

Test plan

• Unit tests for hashOgImageOptions() with componentHash/version params
• E2E test verifying cache directory creation and file storage
• Manual testing in playground

🤖 Generated with Claude Code

[harlan-zw]

Code Review Summary

Reviewed PR #413 for potential bugs and code quality issues.

Result: No high-confidence issues found ✅

All issues identified scored below the 80% confidence threshold for automated reporting. The implementation follows the existing codebase patterns appropriately.

Lower-confidence observations (not actionable)

Issue	Score	Note
JSON.parse without try-catch	72%	Cache written by same module, low corruption risk
Expiry from build time	72%	Reasonable for CI caching with 72hr default
Missing null check on cached.data	42%	Type-safe write path prevents normal occurrence
mkdirSync error handling	28%	Standard CI paths are writable
Test comment/variable name mismatch	25%	Code quality, not functional bug
Pre-existing TODO incomplete	25%	Out of scope for this PR
Hash function inconsistency	15%	simpleHash serves different purpose (URL-safe)

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Automated review by Claude Code