feat: improve nix-update workflow and update packages

- Refactor nix-update.yml: push directly to master instead of PRs
- Add skip list for packages without upstream releases
- Add opencode subpackage handling for node_modules
- Add nix-update-script to beads, code2prompt, mem0
- Update mem0: 1.0.0 -> 1.0.2
- Update opencode: 1.1.18 -> 1.1.25
- Fix n8n tag format
- Add n8n update.sh helper script

pkgs/n8n/update.sh

@@ -0,0 +1,6 @@
+#!/usr/bin/env nix-shell
+#!nix-shell --pure -i bash -p bash curl jq nix-update cacert git
+set -euo pipefail
+
+new_version="$(curl -s "https://api.github.com/repos/n8n-io/n8n/releases/latest" | jq --raw-output '.tag_name | ltrimstr("n8n@")')"
+nix-update n8n --version "$new_version"