feat(openclaw): add runtime closure meta-package for Harmonia caching

Creates openclaw-runtime-closure as a symlinkJoin of all runtime dependencies (nodejs_22, kubectl, jq, git, emacs, tsx, tea, python3.withPackages pymupdf, qmd) that will be pushed to the Harmonia binary cache by CI and pulled into the PVC by the init container at pod startup.

This meta-package enables the thin Docker image architecture where:
- The Docker image stays small (~1.5GB vs 2.7GB) with only /app, nix, and basics
- Runtime deps are fetched from Harmonia at pod startup via nix copy --from
- CI push is fast (thin image) and runtime deps are cached separately

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

packages/default.nix

@@ -10,4 +10,5 @@ rec {
   opencode = pkgs.callPackage ./opencode { };
   qmd = pkgs.callPackage ./qmd { };
   openclaw-image = pkgs.callPackage ./openclaw-image { inherit qmd; };
+  openclaw-runtime-closure = pkgs.callPackage ./openclaw-image/runtime-closure.nix { inherit qmd; };
 }