Add headlamp-plugin-developer agent skill

Extracted from headlamp-sealed-secrets-plugin to serve as the
standalone home for developing Headlamp agent skills.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -0,0 +1,25 @@
+# Headlamp Agent Skills
+
+This repository is the home for developing and maintaining Claude Code agent skills for Headlamp Kubernetes dashboard plugin development.
+
+## Repository Structure
+
+```
+.claude/agents/          # Agent skill definitions (markdown with YAML frontmatter)
+README.md                # Project documentation
+```
+
+## Agent Skill Format
+
+Each skill is a markdown file in `.claude/agents/` with:
+
+1. **YAML frontmatter** — `name`, `description`, `tools`, `model`
+2. **System prompt** — Role and behavioral instructions
+3. **Reference sections** — API docs, patterns, conventions, and code examples
+
+## Guidelines
+
+- Keep skills focused and practical — include API signatures, code patterns, and common pitfalls
+- Use code blocks for all API examples
+- Include test mock patterns where applicable
+- Update skills when Headlamp APIs change