Add Rails 8 examples for GitStore use cases

[Copilot]

Creates three complete Rails 8 example applications demonstrating GitStore's killer use cases: versioned content management, configuration management, and compliance-ready audit trails.

Examples Added

Wiki/CMS (examples/wiki_cms/)

• Page model with GitStore-backed versioning
• Full CRUD with history, diff viewing, rollback
• Markdown renderer with wiki-style [[Page Links]]

Configuration Management (examples/config_management/)

• ConfigEntry model for YAML/JSON configs
• Environment-specific configuration support
• Version history and instant rollback

Audit Trail (examples/audit_trail/)

• AuditedRecord model with SHA-256 integrity checksums
• Point-in-time data reconstruction
• Existence proof generation for compliance
• AuditService for audit report generation

Usage Pattern

# All examples follow this pattern
Rails.application.config.to_prepare do
  repo_path = Rails.root.join('content_repo')
  Rails.application.config.store = GitStore.new(repo_path.to_s)
end

# Model integration
store.transaction("Updated page", author) do
  store["pages/#{slug}.yml"] = page_data
end

Security

• XSS prevention via HTML escaping in views/helpers
• Shell injection protection (array form for system())
• URL validation in markdown (blocks javascript: URLs)
• YAML deserialization safety (no arbitrary Symbol creation)
• CSRF protection documented (requires ApplicationController integration)

Original prompt

Based on the repository information, the killer use case for GitStore is building versioned, content-driven applications where you want the full power of Git's version control applied to your application data.

Here are the standout use cases, write feature-complete examples as complete rails 8 examples:

🚀 1. Content Management Systems / Wikis

This is the primary killer use case. GitStore lets you build wiki-like applications (like the mentioned Shinmun blog engine) where:

• Every edit creates a commit with full history
• You get branching, merging, and rollback for free
• Content can be edited via the app OR directly in Git
• Easy collaboration through standard Git workflows

📝 2. Configuration Management

Store application configs as versioned YAML/JSON files:

• Track who changed what and when
• Roll back bad configurations instantly
• Review config changes via pull requests

🔄 3. Data Auditing & Compliance

For applications requiring a complete audit trail:

• Every data change is a Git commit with timestamp and author
• Immutable history that can't be tampered with
• Easy to reconstruct state at any point in time

💡 Key Differentiator

Unlike traditional databases, GitStore gives you:

• In-memory speed with persistent, versioned storage
• Transaction support with automatic rollback on errors
• Zero infrastructure — it's just Git, which you already know and use

It's essentially "Git as a database" for Ruby applications where version history and human-readable storage matter more than query performance.

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