chore: trim root — drop orphan knip.json, tuck cliff.toml under .github/

- knip.json: orphan config, knip not installed and not referenced
  anywhere. Removed.
- cliff.toml: used only by .github/workflows/deploy-prod.yml at release
  time. Moved to .github/cliff.toml and the workflow's config path
  updated to match. Reduces root clutter on a public docs repo.

Author: Mlaz-code

cliff.toml .github/cliff.tomlcliff.toml renamed to .github/cliff.toml

@@ -171,7 +171,7 @@ jobs:
         uses: orhun/git-cliff-action@f50e11560dce63f7c33227798f90b924471a88b5 # v4
         id: cliff
         with:
-          config: cliff.toml
+          config: .github/cliff.toml
           args: --latest --strip header
         env:
           OUTPUT: CHANGES.md