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/instructions/TEMPLATE.instructions.md

@@ -0,0 +1,19 @@
+---
+description: "Project-specific coding guidance"
+applyTo: "**/*"
+---
+
+# Instruction Template
+
+Use this file as a starting point for workspace instructions.
+
+## Keep
+
+- Rules concrete and testable
+- Scope narrow with `applyTo` where possible
+- Content short to avoid context bloat
+
+## Avoid
+
+- Duplicating skill workflows
+- Vague style statements without actionability