Sync host lists with flake.nix and add CLAUDE.md

Remove the nonexistent kuma host and add the missing linode-minimal
host across README, AGENTS.md, docs, and CI eval workflows so they
match flake.nix's nixosConfigurations. Also add CLAUDE.md with
architecture/safety guidance for future Claude Code sessions.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

docs/flake-lock-automation.md

@@ -11,11 +11,11 @@ and to verify that declared NixOS hosts still evaluate after dependency updates.
 - A separate CI workflow evaluates every configured host before merge:
   - `nixos`
   - `docker`
-  - `kuma`
   - `server`
   - `nix-cache`
   - `nix-minimal`
   - `pxe-boot`
+  - `linode-minimal`
 
 ## Why hosts should stop using `--upgrade-all`