Critical safety and compatibility fixes based on ChatGPT feedback

SAFETY FIXES:
- Add prominent safety warnings for destructive operations
- Add BOOTC_I_KNOW_THIS_WIPES_MY_DISK environment variable checks
- Add safety warnings to manual installation scripts

BUILD FIXES:
- Fix Containerfile systemd calls to use symlinks instead of systemctl
- Replace brittle image validation with podman image mount
- Add fallback for rootless/mount issues

COMPATIBILITY FIXES:
- Align Debian version references (12 Bookworm vs 14 Forky)
- Add comprehensive COMPATIBILITY.md with version matrix
- Add kernel requirements for composefs (5.15+ basic, 6.5+ recommended)
- Document experimental flags and version requirements

TECHNICAL IMPROVEMENTS:
- Use DEBIAN_FRONTEND=noninteractive in build scripts
- Improve image inspection robustness
- Add explicit version testing matrix
- Document known issues and workarounds

This addresses the most critical issues identified in the ChatGPT review:
1. Safety warnings for destructive operations
2. Build-time systemd handling fixes
3. Robust image validation methods
4. Version compatibility documentation

installation.md

@@ -1,5 +1,15 @@
 # Installation
 
+⚠️ **CRITICAL SAFETY WARNING** ⚠️
+
+**bootc installation involves DESTRUCTIVE operations that can WIPE your disk and data!**
+
+- `bootc install to-disk` will **DESTROY** existing partitions and data
+- `grub-install` operations can **CORRUPT** your bootloader
+- Always test on a **virtual machine** or **test hardware** first
+- Never run on production systems without proper backups
+- Use `BOOTC_I_KNOW_THIS_WIPES_MY_DISK=1` environment variable to confirm you understand the risks
+
 ## Base Images
 
 Many users will be more interested in base (container) images for Debian.
@@ -12,7 +22,7 @@ For pre-built base images, any Debian derivative can be converted to use bootc.
 
 ### Prerequisites
 
-- Debian 14 (Forky) or later
+- Debian 12 (Bookworm) or later (tested with Bookworm)
 - Systemd as the init system
 - Root access for installation
 - Development tools and dependencies for compiling bootc