Add wg-mtu-auto initial implementation, documentation, and unit tests

- Added main.py: automatic WireGuard MTU calculation and PMTU probing
- Added test.py: unittests covering base, PMTU, and fallback scenarios
- Added Makefile: includes test target and install guidance
- Added README.md: usage, pkgmgr installation, and MIT license

Reference: https://chatgpt.com/share/68efc179-1a10-800f-9656-1e8731b40546

README.md

@@ -0,0 +1,98 @@
+# wg-mtu-auto
+
+Automatically detect the optimal WireGuard MTU by analyzing your local egress interface and optionally probing the Path MTU (PMTU) to one or more remote hosts.  
+The tool ensures stable and efficient VPN connections by preventing fragmentation and latency caused by mismatched MTU settings.
+
+---
+
+## ✨ Features
+
+- **Automatic Egress Detection** — Finds your primary internet interface automatically.  
+- **WireGuard MTU Calculation** — Computes `wg0` MTU based on egress MTU minus overhead (default 80 bytes).  
+- **Optional Path MTU Probing** — Uses ICMP “Don’t Fragment” (`ping -M do`) to find the real usable MTU across network paths.  
+- **Multi-Target PMTU Support** — Test multiple remote hosts and choose an effective value via policy (`min`, `median`, `max`).  
+- **Dry-Run Mode** — Simulate changes without applying them.  
+- **Safe for Automation** — Integrates well with WireGuard systemd services or Ansible setups.
+
+---
+
+## 🚀 Installation
+
+### Option 1 — Using [pkgmgr](https://github.com/kevinveenbirkenbach/package-manager)
+
+If you use Kevin Veen-Birkenbach’s package manager (`pkgmgr`):
+
+```bash
+pkgmgr install automtu
+````
+
+This will automatically fetch and install `wg-mtu-auto` system-wide.
+
+### Option 2 — Run directly from source
+
+Clone this repository and execute the script manually:
+
+```bash
+git clone https://github.com/kevinveenbirkenbach/wg-mtu-auto.git
+cd wg-mtu-auto
+sudo python3 main.py --help
+```
+
+---
+
+## 🧩 Usage Examples
+
+### Basic detection (no PMTU)
+
+```bash
+sudo automtu
+```
+
+### Specify egress interface and force MTU
+
+```bash
+sudo automtu --egress-if eth0 --force-egress-mtu 1452
+```
+
+### Probe multiple PMTU targets (safe policy: `min`)
+
+```bash
+sudo automtu --pmtu-target 46.4.224.77 --pmtu-target 2a01:4f8:2201:4695::2
+```
+
+### Choose median or max policy
+
+```bash
+sudo automtu --pmtu-target 46.4.224.77,1.1.1.1 --pmtu-policy median
+sudo automtu --pmtu-target 46.4.224.77,1.1.1.1 --pmtu-policy max
+```
+
+### Dry-run (no system changes)
+
+```bash
+automtu --dry-run
+```
+
+---
+
+## 🧪 Development
+
+Run unit tests using:
+
+```bash
+make test
+```
+
+To see installation guidance (does not install anything):
+
+```bash
+make install
+```
+
+---
+
+## 👤 Author
+
+**Kevin Veen-Birkenbach**
+[https://www.veen.world](https://www.veen.world)
+