docs: add Mermaid architecture diagram to README

[zanni098]

Problem

The README and docs lack a visual architecture diagram. The ARCHITECTURE.md has a pipeline diagram in text, but there is no visual diagram in the README that shows how the components fit together.

Proposed Solution

Add a Mermaid architecture diagram to README.md showing:

1. Discovery sources (OpenAPI, HAR, Browser, mitmproxy)
2. Core pipeline (Spec parsing, Archetype detection, Generation)
3. Output targets (Python, Go, Rust, TS, MCP, Skills)
4. Quality layer (Scorecard, Proof, shipcheck)
5. Web UI and Catalog

Also add the diagram to docs/ARCHITECTURE.md as a renderable Mermaid block.

Acceptance Criteria

• Mermaid diagram in README.md
• Same diagram in docs/ARCHITECTURE.md
• Diagram renders correctly on GitHub
• Diagram covers all major components

[sashwatpuri]

Hi! I'd like to take this issue.

I'll add a renderable Mermaid architecture diagram to both README.md and docs/ARCHITECTURE.md, covering the discovery sources, core pipeline, generated output targets, quality layer, Web UI, and Catalog.

I'll keep the diagram consistent with the existing architecture documentation and verify that it renders correctly on GitHub.

[zanni098]

Sounds great! The existing ARCHITECTURE.md has the pipeline breakdown already - a Mermaid diagram that ties all the components together would be really helpful for newcomers. Go ahead and open a PR whenever you are ready.