Add exercises and setup instructions for AI-powered agents in SDLC workshop

[kavyashri-as]

• Created Exercise 3: Build GitHub Actions Workflow with CI/CD automation for Helpdesk CRM.
• Created Exercise 4: Self-Healing Workflow in Action to observe automated dependency fixes.
• Added Readme.md for workshop overview, exercises, and learning outcomes.
• Added SetupInstructions.md for initial setup of the Help Desk application.
• Created Stage 1 to Stage 4 documentation for CLI, SDK, MCP agents, and multi-agent workflows.
• Added images for branch creation and delegation started.

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