Nest related configuration options

Group related configuration options into nested TOML sections rather than using flat key-value pairs. This improves readability, maintainability, and makes relationships between settings more explicit.

Example: Instead of:

word-completion = true
word-completion-trigger-length = 7

Use:

[word-completion]
enable = true
trigger-length = 7

This approach:

• Makes configuration hierarchies clear
• Groups related settings together
• Reduces naming conflicts and redundancy
• Improves configuration file organization
• Makes it easier to add related options in the future

When adding new configuration options, consider if they logically belong in an existing section or warrant creating a new nested section.