feat: add agent skills for Claude Code and GitHub Copilot

.claude/skills/README.md

@@ -0,0 +1,57 @@
+# Claude Code Skills for Spec-Driven Development
+
+This directory contains Agent Skills for Claude Code that implement the Spec-Driven Development (SDD) workflow.
+
+## Available Skills
+
+### sdd-1-generate-spec
+
+Generate a comprehensive specification for a feature with workflow guidance and scope validation.
+
+**When to use:** Starting a new feature or enhancement; need to transform an initial idea into a structured specification.
+
+### sdd-2-generate-task-list
+
+Convert a specification into an actionable task list with demoable units and detailed subtasks.
+
+**When to use:** After creating a specification; need to break down the work into implementable tasks.
+
+### sdd-3-manage-tasks
+
+Execute structured task implementation with built-in verification and progress tracking.
+
+**When to use:** During implementation; need guided execution with checkpoints and proof artifacts.
+
+### sdd-4-validate-implementation
+
+Validate implementation against the specification using proof artifacts and evidence-based coverage.
+
+**When to use:** After completing implementation; need to verify all requirements are met before shipping.
+
+## Installation
+
+These skills are designed for use with Claude Code. To install:
+
+```bash
+# Copy to user skills directory (available in all projects)
+mkdir -p ~/.claude/skills
+cp -r .claude/skills/* ~/.claude/skills/
+
+# Or copy to project-specific location (available only in this project)
+# Skills are already in .claude/skills/ for this project
+```
+
+## How Skills Work
+
+Claude Code automatically discovers and can invoke these skills when they're relevant to your workflow. Each skill:
+
+- Contains YAML frontmatter with metadata (name, description, tags)
+- Includes detailed instructions and context markers
+- Provides workflow integration guidance
+- Implements validation and quality checks
+
+## Learn More
+
+- [Claude Code Skills Documentation](https://code.claude.com/docs/en/skills)
+- [SDD Workflow Overview](https://github.com/liatrio-labs/spec-driven-workflow)
+- [SDD Playbook](https://liatrio-labs.github.io/spec-driven-workflow/)