feat: Add new agents and skills for Docker, TestLink, and OpenWrt

- Introduced "Docker Build & Test Engineer" agent for building and testing Docker images.
- Added "TestLink Autotest Engineer" agent for generating and verifying autotests from TestLink cases.
- Created "Branch Review Engineer" agent for reviewing branch diffs and proposing improvements.
- Developed "OpenWrt VPN & Network Engineer" agent for designing and implementing OpenWrt networking with VPN.
- Established a structured directory for agents, skills, prompts, instructions, and hooks under `.github/`.
- Implemented detailed skills for branch review processes, including reading code, analyzing improvements, and applying changes.
- Added skills for OpenWrt network discovery, VPN routing, and hardening.
- Created README files for better documentation and navigation of the repository structure.

.github/skills/openwrt-network-hardening/SKILL.md

@@ -0,0 +1,59 @@
+---
+name: openwrt-network-hardening
+description: "Harden and verify OpenWrt VPN deployment with fail-closed routing, DNS leak prevention, and operational checks for split tunneling/GeoIP/ASN rules. Use when: openwrt hardening, vpn leak prevention, kill switch openwrt, verify split tunnel, validate geoip/asn policy."
+argument-hint: "Applied or planned OpenWrt VPN configuration"
+---
+
+# OpenWrt Network Hardening
+
+Finalize reliability, security, and day-2 operations after VPN routing setup.
+
+## Procedure
+
+### Step 1 - Fail-Closed and Leak Controls
+
+Define controls:
+- kill-switch or fail-closed path for protected traffic
+- DNS leak prevention between WAN and tunnel
+- default-deny posture for sensitive tunnel-marked flows
+
+### Step 2 - Service Robustness
+
+Set:
+- service dependency ordering
+- restart policies
+- health-check commands
+- basic rollback strategy
+
+### Step 3 - Monitoring and Troubleshooting
+
+Provide checks for:
+- tunnel up/down state
+- route-policy correctness
+- packet counters for expected rule hits
+- endpoint reachability and latency
+
+### Step 4 - Operational Runbook
+
+Document:
+- what to verify after reboot
+- what to verify after package upgrades
+- how to rotate endpoints or credentials safely
+
+## Output Format
+
+```md
+## Hardening and Verification
+
+### Controls Applied
+- ...
+
+### Health Checks
+- ...
+
+### Runbook
+- ...
+
+### Rollback
+- ...
+```