feat(KB-503): add multi-project CLI support with project subcommands

- Add project subcommands: list, add, remove, show, set-default, detect
- Add --project flag support for all task commands
- Create project-context.ts utilities for project resolution
- Add defaultProjectId to GlobalSettings type
- Implement project auto-detection from cwd
- Update CLI argument parsing for global --project flag
- Add multi-project CLI documentation to AGENTS.md

packages/dashboard/app/components/SetupWizard.tsx

@@ -396,7 +396,7 @@ export function SetupWizard({ isOpen, onClose, onProjectCreated, onRegisterProje
               <button
                 className="btn btn-primary"
                 onClick={handleValidate}
-                disabled={state.isValidating || !!state.validationError}
+                disabled={state.isValidating || state.validationError}
               >
                 {state.isValidating ? (
                   <>