[Feature]: Add Agent Skill Support (Universal, Claude Code, Codex)

[LRriver]

Issue Title

[Feature Request]: Add Agent Skill integrations (Universal, Claude Code, and Codex formats) for serverless PPT generation

Description

Overview

Currently, using AIPPT typically requires users to deploy and run the project locally or on a server. However, most generation scripts and templates in this repository can naturally serve as execution workflows and reference files for AI coding agents and LLM skills.

We propose adding structured Skill configurations in three standardized formats:

1. Universal Skill Format: Standardized system instructions and execution templates compatible with general LLM agent frameworks.
2. Claude Code Format: Tailored configuration (e.g., CLAUDE.md or Claude-specific skill structure) for direct invocation inside Claude Code.
3. Codex / Code Agent Format: Agent tool and workflow definitions optimized for OpenAI Codex / code assistant workflows.

Motivation & Value

• Zero Deployment Friction: Users will no longer need to deploy a standalone backend service to generate slides.
• Agentic PPT Generation: Users can plug these skills directly into tools like Claude Code or Codex, allowing the agent to read existing project scripts as reference tools and orchestrate PPT generation end-to-end.
• Broader Reach: Retains the existing project architecture while extending its capability to agent ecosystems.

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Proposed Implementation & Task List

• Directory Structuring: Create a dedicated skills/ directory to house reference scripts, templates, and agent definitions without altering core project logic.
• Universal Skill Definition:
  • Create a modular specification (skills/universal/) outlining input schemas, step-by-step PPT construction logic, and output validation.
• Claude Code Integration:
  • Provide a ready-to-use setup (skills/claude-code/ or workspace guidelines) configuring reference scripts as tool definitions.
• Codex / Code Agent Integration:
  • Define prompt templates and execution guidelines (skills/codex/) optimized for Codex tool use and terminal-based script execution.
• Documentation:
  • Add a dedicated section to README.md explaining how to import and trigger these skills inside Codex and Claude Code.

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Additional Context

The underlying script logic remains unchanged; the skills will primarily act as orchestration adapters and prompt/tool layers referencing the existing codebase.