Fix critical build pipeline and update documentation

CRITICAL FIXES:
- Fix build-initramfs.sh early exit preventing zinit installation
- Add binary detection/installation logic to setup-initramfs.sh
- Ensure compiled components are properly installed to initramfs

DOCUMENTATION:
- Update README.md to reflect actual implementation
- Document source compilation approach with git submodules
- Add development workflow and caching documentation
- Remove outdated GitHub releases references

This fixes the 'zinit not found' boot error by ensuring the build
pipeline completes all phases including initramfs assembly.

scripts/build-initramfs.sh

@@ -42,7 +42,6 @@ echo "[+] Compiling Zero-OS components..."
 if [ -f /build/scripts/build-smart.sh ]; then
     # Use smart build if available (with caching)
     /build/scripts/build-smart.sh
-    exit $?
 else
     # Fallback to direct component compilation
     /build/scripts/compile-components.sh