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>

AGENTS.md

@@ -9,11 +9,11 @@ The flake currently exposes these NixOS configurations:
 
 - `nixos`
 - `docker`
-- `kuma`
 - `server`
 - `nix-cache`
 - `nix-minimal`
 - `pxe-boot`
+- `linode-minimal`
 
 Do not deploy, switch, reboot, repartition, format disks, or run destructive
 install commands from this repository unless explicitly asked.