[plan] Document local testing workflows without GitHub Actions

[github-actions]

Objective

Create comprehensive documentation for testing workflows locally without pushing to GitHub Actions, reducing feedback loop from minutes to seconds.

Context

Currently only 7 documentation references exist for local testing. Developers may need to push to GitHub Actions to test workflows, creating a slow feedback loop (2-5 minutes vs <1 second locally). The repository has 42 mock files suggesting testing infrastructure exists, but usage is not well documented.

Approach

1. Create docs/guides/local-testing.md guide
2. Document --no-emit flag and validation-only mode
3. Explain --watch mode for rapid iteration
4. Show how to test MCP server configurations locally
5. Document mock/stub usage for GitHub API calls (leverage 42 existing mock files)
6. Demonstrate testing workflow fragments independently
7. Include troubleshooting section for common local testing issues
8. Provide comparison table: local testing vs GitHub Actions testing
9. Link guide from README.md under "Development" section

Guide Structure

# Local Workflow Testing Guide

## Overview
Test workflows in seconds, not minutes, without GitHub Actions.

## Quick Testing Methods

### 1. Validation-Only Mode
`gh-aw compile workflow.md --no-emit`

### 2. Watch Mode for Iteration  
`gh-aw compile workflow.md --watch`

### 3. Testing Workflow Fragments
[How to test shared fragments independently]

### 4. Mocking GitHub Context
[How to use the 42 mock files]

### 5. MCP Server Local Testing
[Local MCP server testing strategies]

## Comparison: Local vs GitHub Actions

| Aspect | Local Testing | GitHub Actions |
|--------|---------------|----------------|
| Feedback Time | <1 second | 2-5 minutes |
| Cost | Free | Consumes Actions minutes |
| Internet Required | No | Yes |
| Full Integration Test | No | Yes |

## When to Use Each Method
- Local: Syntax, validation, rapid iteration
- GitHub Actions: Integration testing, production deployment

Files to Create/Modify

• Create: docs/guides/local-testing.md
• Update: README.md (add link to guide)

Acceptance Criteria

• Guide explains --no-emit flag and validation-only mode
• Documents --watch mode for rapid iteration
• Shows MCP server local configuration testing
• Explains mock/stub usage for GitHub API calls
• Demonstrates testing workflow fragments independently
• Includes troubleshooting section for common issues
• Provides comparison table: local vs GitHub Actions testing
• Linked from README.md under "Development" section
• Examples use actual mock files from repository

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AI generated by Planning Assistant for #7631
Related to #8056

AI generated by Plan Command for discussion #7631