meta: add AI agent rules and skills

Create a modular, context-aware style guide for AI code assistants.

- Add nixos-architecture skill for .nix file generation and networking patterns
- Add dns-management rule to enforce Bind9 SOA serial increments
- Add cicd-networking rule for direct-IP runner authentication
- Add git-workflow rule to enforce conventional and atomic commits

.agent/rules/git-workflow.md

@@ -0,0 +1,21 @@
+---
+name: git-workflow
+description: Rules for generating Git commit messages and managing branch workflows.
+globs: ["COMMIT_EDITMSG", ".git/*"]
+---
+
+# Git Workflow Constraints
+
+When generating commit messages, reviewing code for a commit, or planning a branch workflow, strictly follow these standards:
+
+1. **Commit Formatting**
+   - **Conventional Commits**: You MUST format all commit messages using conventional prefixes: `feat:`, `fix:`, `docs:`, `refactor:`, `ci:`, `meta:`.
+   - **Clarity**: Ensure the message clearly explains *what* changed and *why*.
+2. **Atomic Commits**
+   - Group changes by a single logical concern.
+   - NEVER mix documentation updates, core infrastructure code, and style guide changes in the same commit.
+   - Ensure that the generated commit is easily revertible without breaking unrelated features.
+3. **Branching Workflow**
+   - Always assume changes will be pushed to a feature branch to create a Pull Request.
+   - Do not suggest or generate commands that push directly to the main branch.
+