add woodpecker-peek input + cache to attic via CI

Re-exposes oleks/woodpecker-peek as packages.<sys>.woodpecker-peek for
x86_64-linux and aarch64-linux, and adds it to ci/build.py so the
amd64/arm64 workflows push the closure to attic-infra-cache-k3s-1.
Consumers (emmett) then set services.woodpecker-peek.package = pkgs.woodpecker-peek
and pull the cached binary instead of rebuilding.

flake.nix

@@ -33,6 +33,13 @@
       url = "github:retif/stalewood";
       inputs.nixpkgs.follows = "nixpkgs";
     };
+
+    # woodpecker-peek — tray app for Woodpecker CI (on git.oleks.space).
+    # Re-exposed so flake-hub CI warms attic and emmett pulls cached.
+    woodpecker-peek = {
+      url = "git+https://git.oleks.space/oleks/woodpecker-peek?ref=main";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
   };
 
   outputs =
@@ -45,6 +52,7 @@
       antigravity-nix,
       nix-deps,
       stalewood,
+      woodpecker-peek,
       ...
     }:
     let
@@ -115,6 +123,10 @@
           # stalewood — re-exposed from its own flake. No s390x output,
           # so it rides the same native-only gate.
           stalewood = stalewood.packages.${sys}.default;
+          # woodpecker-peek — same pattern; consumers (emmett) read the
+          # attic-cached binary via flake-hub's overlay, then set
+          # services.woodpecker-peek.package = pkgs.woodpecker-peek;.
+          woodpecker-peek = woodpecker-peek.packages.${sys}.default;
         };
 
       # Overlay providing Hyprspace. Requires `pkgs.hyprland` to be present