Added --ai option to prevent interactive AI selection

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: lubatti

README.md

@@ -84,9 +84,9 @@ Run directly without installing:
 uvx --from git+https://github.com/github/spec-kit.git specify init <PROJECT_NAME>
 
 # Or initialize in existing project
-uvx --from git+https://github.com/github/spec-kit.git specify init .
+uvx --from git+https://github.com/github/spec-kit.git specify init . --ai claude
 # or
-uvx --from git+https://github.com/github/spec-kit.git specify init --here
+uvx --from git+https://github.com/github/spec-kit.git specify init --here --ai claude
 ```
 
 **Benefits of persistent installation:**