create_base_onboarding

When discovery finds * * zero * * bases under any VS Code workspace folder ( root or child ),
the extension prompts the user to create a reqlan base at the workspace-folder root.
Do not auto-create `.reqlan`. Command `reqlan.createBase` creates `<folder>/.reqlan/`
( empty directory is a valid marker ), rediscovers, and activates indexing for that base.
With multiple workspace folders and no bases, prompt against the first folder.
Headless create-base helper: create-base.ts ( also used by CLI `init` ).

Interactive page: create_base_onboarding