Mem-Client: New MDS Folder Requires index + stories

New MDS component folders must include index and stories files.

Rationale:
- Standard entry and story coverage make components easier to consume and review.

Scope:
- PR review policy for new folders under `domains/frontend/mem-client/src/mds/components/**`.

Trigger:
- A PR creates a new component folder in scope and adds at least one component implementation file (`*.tsx`, excluding stories/style files).

Approval checks:
1) Folder includes `index.ts`.
2) Folder includes at least one `*.stories.tsx` file.

Evidence:
- Diff shows required files in the same folder.

Decision:
- Return NOT APPROVED when trigger is met and either required file is missing.