docs: add contributor guide and compatibility matrix

README.md

@@ -22,6 +22,20 @@ Current version: `v0.1.0`.
 - `sudo` / root privileges
 - Internet access for downloading binaries/artifacts
 
+## Compatibility matrix
+
+| Environment | Status | Notes |
+|---|---|---|
+| Ubuntu / Debian | ✅ Supported | Primary target for initial MVP (`apt`) |
+| Alma / Rocky / RHEL-family | ⚠️ Partial | Planned support paths exist, but this release focuses on core workflow verification |
+| Arch Linux | ⚠️ Partial | Generic support path in architecture, not fully validated in this release |
+| Fedora | ⚠️ Partial | Generic support path in architecture, not fully validated in this release |
+| `yum` / `dnf` | ⚠️ Partial | Service/dependency handling is planned for full parity |
+| `pacman` | ⚠️ Partial | Detection and abstraction are present, full validation pending |
+| `tmux` | ✅ Supported | Required for `tmux-systemd` mode |
+| `screen` | ✅ Supported | Optional service transport |
+| `systemd` | ✅ Supported | Required for autostart service modes |
+
 ## Supported cores
 
 | Core | Default directory | Default port | Runtime | Protocol | Notes |
@@ -204,3 +218,7 @@ sudo bash install.sh --version
 ## Changelog
 
 See [`CHANGELOG.md`](CHANGELOG.md).
+
+## Contributing
+
+Please read [`CONTRIBUTING.md`](CONTRIBUTING.md).