Add CUB package builder and include in all Red Bear OS configs

CUB (Red Bear OS Package Builder) is a Rust CLI tool that combines package management and building:
- RBPKGBUILD parser (TOML format) with full spec support
- Cookbook adapter converting RBPKGBUILD to recipe.toml
- PKGBUILD (Arch AUR) to RBPKGBUILD conversion with Linuxism detection
- Dependency mapping (Arch to Redox names)
- pkgar package creation integration
- Build environment setup with Cookbook env vars
- CLI with pacman-style shortcuts: -S, -Ss, -B, -G, -Pi, -Sua, -Sc, --import-aur

28 cub-lib tests passing. cub-cli compiles with local pkgutils.
Added cub = {} to redbear-desktop, redbear-full, redbear-minimal configs.
Created recipe symlink and updated integrate-redbear.sh.

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

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

local/scripts/integrate-redbear.sh

@@ -154,6 +154,7 @@ symlink "../../local/recipes/system/redbear-meta" "recipes/system/redbear-meta"
 symlink "../../local/recipes/system/udev-shim" "recipes/system/udev-shim"
 symlink "../../local/recipes/core/ext4d" "recipes/core/ext4d"
 symlink "../../local/recipes/tui/mc" "recipes/tui/mc"
+symlink "../../local/recipes/system/cub" "recipes/system/cub"
 status "Custom recipe symlinks ready"
 echo ""