ci: evaluate hosts discovered from the flake, not a hard-coded list

The eval steps listed hosts by hand and still referenced lyrathorpe-x1c,
which was removed (replaced by t400/macpro31), so CI errored. Derive the
NixOS and Darwin host lists from attrNames of nixos/darwinConfigurations
instead, so adding or removing a host needs no workflow change.

Verified locally under bash: all current hosts (edaas, macpro31, mbp,
t400, mac) evaluate; no removed host is referenced.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitea/workflows/ci.yaml

@@ -34,10 +34,16 @@ jobs:
       # Evaluate (not build) each host's toplevel so eval errors fail CI cheaply.
       # aarch64 / darwin hosts evaluate fine on an x86_64 runner; only building
       # would need emulation, which we deliberately avoid here.
+      #
+      # Host lists are discovered from the flake (attrNames of
+      # nixos/darwinConfigurations) rather than hard-coded, so adding or removing
+      # a host needs no change to this workflow.
       - name: Evaluate NixOS host configurations
         run: |
           set -euo pipefail
-          for host in lyrathorpe-mbp lyrathorpe-x1c emmathorpe-edaas; do
+          hosts=$(nix eval --raw '.#nixosConfigurations' \
+            --apply 'cfgs: builtins.concatStringsSep "\n" (builtins.attrNames cfgs)')
+          for host in $hosts; do
             echo "::group::eval $host"
             nix eval --raw ".#nixosConfigurations.$host.config.system.build.toplevel.drvPath"
             echo
@@ -47,7 +53,9 @@ jobs:
       - name: Evaluate Darwin host configurations
         run: |
           set -euo pipefail
-          for host in lyrathorpe-mac; do
+          hosts=$(nix eval --raw '.#darwinConfigurations' \
+            --apply 'cfgs: builtins.concatStringsSep "\n" (builtins.attrNames cfgs)')
+          for host in $hosts; do
             echo "::group::eval $host"
             nix eval --raw ".#darwinConfigurations.$host.config.system.build.toplevel.drvPath"
             echo