Fix: npm ERR! 403 Forbidden when installing claude-flow in GitHub Codespaces

## Problem
When trying to install or run `claude-flow@alpha` in GitHub Codespaces, users encounter a 403 Forbidden error:

```
npm ERR! code E403
npm ERR! 403 403 Forbidden - GET https://registry.npmjs.org/claude-flow
npm ERR! 403 In most cases, you or one of your dependencies are requesting
npm ERR! 403 a package version that is forbidden by your security policy, or
npm ERR! 403 on a server you do not have access to.
```

## Environment
- GitHub Codespaces
- npm registry: https://registry.npmjs.org/
- Package: claude-flow@alpha (v2.0.0-alpha.91)

## Root Cause
GitHub Codespaces appears to have security policies that block certain packages or dependencies from the npm registry, specifically affecting `@modelcontextprotocol/sdk` which is a dependency of claude-flow.

## Solution
Use the yarn registry instead of npm registry, which doesn't have the same restrictions in Codespaces.

### Method 1: Global Installation via Yarn Registry
```bash
# Switch npm to use yarn registry
npm config set registry https://registry.yarnpkg.com

# Install claude-flow globally
npm install -g claude-flow@alpha

# Restore npm registry (optional)
npm config set registry https://registry.npmjs.org
```

### Method 2: Configure npmrc for npx
```bash
# Create .npmrc with yarn registry
cat > ~/.npmrc << 'EOF'
registry=https://registry.yarnpkg.com
EOF

# Now npx works
npx claude-flow@alpha --version
```

### Method 3: Use Local flow-nexus Alternative
For projects with flow-nexus locally available:
```bash
cd flow/mcp-server
npm install --production
npm link

# Create claude-flow wrapper
cat > ~/claude-flow << 'EOF'
#!/bin/bash
flow-nexus "$@"
EOF
chmod +x ~/claude-flow
sudo mv ~/claude-flow /usr/local/bin/claude-flow
```

## Verification
After applying the fix:
```bash
$ claude-flow --version
v2.0.0-alpha.91

$ npx claude-flow@alpha sparc modes
✅ Available SPARC Modes:
...
```

## Additional Notes
- The yarn registry (https://registry.yarnpkg.com) serves as a reliable mirror
- This issue specifically affects GitHub Codespaces environments
- The package and all dependencies install correctly from the yarn registry

## Related
- Affects users trying to use claude-flow in GitHub Codespaces
- May affect other packages with similar dependencies

Start by reproducing the npm installation in GitHub Codespaces with claude-flow@alpha and compare the npm and yarn registry configurations shown in the issue. Review the ~/.npmrc setup and the flow/mcp-server alternative, then determine whether a repository change is possible and verify installation with claude-flow --version and the documented npx command.

Written by the indexing model from the issue text.