docs: retarget README org links to main after .github PRs merge

[surrealwolf]

Context

PR #6 links org docs from the README using interim URLs:

• Branding → already on main
• Project setup → DataKnifeAI/.github#5
• Naming → DataKnifeAI/.github#3
• Repo settings → DataKnifeAI/.github#4

Acceptance

After those .github PRs merge (or equivalent docs land on main):

• Replace PR URLs with https://github.com/DataKnifeAI/.github/blob/main/docs/... paths
• Keep the org-context line concise