Add Arch Linux expert resources

instructions/debian-linux.instructions.md

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+---
+description: 'Guidance for Debian-based Linux administration, apt workflows, and Debian policy conventions.'
+applyTo: '**'
+---
+
+# Debian Linux Administration Guidelines
+
+Use these instructions when writing guidance, scripts, or documentation intended for Debian-based systems.
+
+## Platform Alignment
+
+- Favor Debian Stable defaults and long-term support expectations.
+- Call out the Debian release (`bookworm`, `bullseye`, etc.) when relevant.
+- Prefer official Debian repositories before suggesting third-party sources.
+
+## Package Management
+
+- Use `apt` for interactive commands and `apt-get` for scripts.
+- Inspect packages with `apt-cache policy`, `apt show`, and `dpkg -l`.
+- Use `apt-mark` to track manual vs. auto-installed packages.
+- Document any apt pinning in `/etc/apt/preferences.d/` and explain why.
+
+## Configuration & Services
+
+- Store configuration under `/etc` and avoid modifying `/usr` files directly.
+- Use systemd drop-ins in `/etc/systemd/system/<unit>.d/` for overrides.
+- Prefer `systemctl` and `journalctl` for service control and logs.
+- Use `ufw` or `nftables` for firewall guidance; state which is expected.
+
+## Security
+
+- Account for AppArmor profiles and mention adjustments if needed.
+- Recommend least-privilege `sudo` use and minimal package installs.
+- Include verification commands after security changes.
+
+## Deliverables
+
+- Provide commands in copy-paste-ready blocks.
+- Include validation steps after changes.
+- Offer rollback steps for destructive actions.