Problem

The current documentation focuses primarily on greenfield/new projects created with specify init <PROJECT_NAME>. Users with existing codebases may not realize that Spec Kit can be used for brownfield/iterative development.

The CLI already supports initializing in existing projects via specify init . or specify init --here, but this isn't prominently shown in the getting started section.

Proposed Solution

Add the existing project commands directly in the installation section where users first learn to use the tool:

# Create new project
specify init <PROJECT_NAME>

# Or initialize in existing project
specify init . --ai claude
# or
specify init --here --ai claude

# Check installed tools
specify check