Configurable grouped drift rendering

tfplan2md now turns Terraform drift into a concise, grouped review section instead of
repeating the same transition for every affected resource.

✨ Features

• Drift entries with the same resource type, attribute path, before value, and after
  value are grouped in a collapsible entry with their resource addresses listed below.
• The new --drift option controls visibility: all (the default), relevant (only
  resources with visible planned changes), or none.
• relevant excludes Terraform no-op changes, and drift entries with different value
  transitions remain separate rather than being combined.

📸 Screenshot

▶️ Getting started

# Show all grouped drift entries (the default)
tfplan2md plan.json --drift all

# Keep only drift for resources with displayed planned changes
tfplan2md plan.json --drift relevant

# Omit the drift section
tfplan2md plan.json --drift none

🔗 Commits

• 3ed79bf7 feat: add configurable grouped drift rendering
• 6b95e9b5 fix: escape line breaks in grouped drift details
• ccf59c04 fix: exclude unchanged attributes from drift groups