fix: Align mcp-tester with WASM MCP server implementations

[guyernest]

Summary

This PR aligns the mcp-tester tool with WASM MCP server implementations, ensuring both Cloudflare Workers and Fermyon Spin deployments work correctly with comprehensive testing support.

Changes

🔧 MCP Tester Improvements

• Fixed JSON-RPC notification handling by detecting absence of 'id' field in requests
• Added verbose flag support (--verbose) for detailed test output
• Fixed scenario executor assertions to properly handle null error fields
• Modified scenario executor to return actual tool response content instead of debug strings

🏗️ WASM Server Architecture

• Separated platform-specific implementations:
  • Cloudflare Workers wrapper using worker crate
  • Fermyon Spin wrapper using spin-sdk
  • Both share the same WasmMcpServer core logic
• Fixed HTTP transport to handle empty 200 responses without Content-Type headers

🧪 Testing Infrastructure

• Created comprehensive scenario test files:
  • calculator-simple.json - Basic arithmetic operations
  • calculator-test.yaml - Full test suite with error cases
  • minimal-test.json - Quick connectivity check
• All scenarios now pass on both deployment platforms

📚 Documentation Updates

• Updated all README files with scenario testing instructions
• Used placeholder URLs (<your-worker-name>, <your-app-name>) for user deployments
• Added clear instructions for users to deploy their own instances

Test Results

Both deployment platforms now pass all tests:

╔════════════════════════════════════════════════════════════╗
║              MCP SERVER TESTING TOOL v0.1.0               ║
╚════════════════════════════════════════════════════════════╝

SUMMARY
════════════════════════════════════════════════════════════
| Total Tests | 14    |
| Passed      | 14    |

Overall Status: PASSED

Testing

Test with mcp-tester after deploying your own instance:

# Cloudflare deployment
./target/release/mcp-tester scenario \
  https://<your-worker-name>.workers.dev \
  examples/wasm-mcp-server/test-scenarios/calculator-test.yaml

# Fermyon deployment  
./target/release/mcp-tester scenario \
  https://<your-app-name>.fermyon.app/ \
  examples/wasm-mcp-server/test-scenarios/calculator-test.yaml

Deploy Your Own

Cloudflare Workers

cd examples/wasm-mcp-server/deployments/cloudflare
make deploy
# Your instance: https://<your-worker-name>.workers.dev

Fermyon Spin

cd examples/wasm-mcp-server/deployments/fermyon-spin
spin deploy
# Your instance: https://<your-app-name>.fermyon.app/

🤖 Generated with Claude Code