feat: add perles to CI binary cache

Extract shared package definition, add to flake packages output
and CI workflow so perles gets built and cached by Harmonia.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/perles/default.nix

@@ -0,0 +1,25 @@
+# Perles - Terminal UI for beads issue tracking
+# Takes src as argument so it can be called from both overlay and flake packages
+{ lib
+, buildGoModule
+, src
+, version ? "unknown"
+}:
+
+buildGoModule {
+  pname = "perles";
+  inherit version src;
+  doCheck = false;
+  vendorHash = "sha256-A5LE9Cor/DRcJtVpiScSoqDYhJIKyaq0cbK+OGmr4XU=";
+
+  ldflags = [
+    "-X main.version=${version}"
+  ];
+
+  meta = with lib; {
+    description = "Perles - Terminal UI for beads issue tracking";
+    homepage = "https://github.com/zjrosen/perles";
+    license = licenses.mit;
+    mainProgram = "perles";
+  };
+}