docs(agents): add AI-assisted development guidance

[antsukanova]

Description

• Add a single starting point for contributors and AI tools to understand project setup, development commands, testing, code review, and release behavior.
• Add an architecture guide that explains how SDP moves from parsing to typed models and back to serialized output.
• Keep generated API documentation separate from contributor guides so documentation commands cannot remove maintained content.
• Include the new guides in formatting and spell checks.

This is a documentation and development-tooling change. It does not change runtime behavior or the public API.

This change implements...

• A new feature
• A bug fix
• Other: AI-assisted development documentation and tooling

Is this a breaking change?

• Yes
• No

I certify that...

• All relevant unit and integration tests have passed and/or have been updated according to this change.

Generative AI (GAI) Usage Disclosure

• Cisco approved GAI tool/IDE was used for coding
• No GAI - Code was written entirely manually without GAI assistance

If a GAI tool/IDE was used then select the category that best describes GAI usage in this PR:

• Manual Draft with GAI Refinement
• GAI Draft with Manual Customization
• GAI Generated Code

Additional GAI Usage Details (Optional):

Cursor was used to draft repository guidance and documentation. The resulting content was reviewed and manually refined.