Document how to create a first LoopGate spec

[rxdt]

Goal

Add a short docs page or README section that shows a newcomer how to turn a project idea into a first docs/specs/*.md file.

Scope

• Use the existing docs/specs/base.md template as the source of truth.
• Include one small example spec for a frontend app change.
• Keep the guidance concise and beginner-friendly.

Acceptance criteria

• The docs mention where docs/plan.md, docs/specs/, and docs/PROJECT_STATUS.md fit.
• The change is documentation-only.
• pnpm gate passes.