docs: Add a "design patterns" section to docs

[dsyme]

Read all the workflows in https://github.com/githubnext/agentics and .github/workflows/*.md in this repo. Synthesize out 4 or 5 major design patterns being used across the different kinds of agentic workflows.

[pelikhan]

And add them to instructions.md too

[dsyme]

We have some new guides, that's enough for now