fix(mcp): support streamable HTTP alias, request-response mode and integration tests

[afjcjsbx]

📝 Description

This PR introduces two distinct and major improvements to the project: a generalized Docker-backed integration testing framework, and enhancements/refactoring for the MCP transport configuration.

1. General Docker-Backed Integration Test Framework

• Introduced a flexible, auto-discovering integration test framework under the integration/ directory.
• This allows developers to easily add integration tests of any kind by simply creating a new suite folder containing a suite.env and docker-compose.yml (no CI workflow edits required).
• Added the integration job to GitHub Actions (build.yml and pr.yml) to automatically run these suites.
• Added a make integration-test command for local execution.
• Includes the first suite (mcp-streamable) as a reference implementation.

2. MCP Transport Refactoring & streamable-http

• Officially supported streamable-http as an explicit alias for the http transport type.
• Centralized and deduplicated transport inference/normalization logic into pkg/config/mcp_transport.go (NormalizeMCPTransportType and EffectiveMCPTransportType).
• Fixed compatibility issues in manager.go by cleanly disabling the standalone SSE GET listener for http/streamable-http transports, accommodating servers that only support streamable POST request-response modes.

🗣️ Type of Change

• 🐞 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 📖 Documentation update
• ⚡ Code refactoring (no functional changes, no api changes)

🤖 AI Code Generation

• 🤖 Fully AI-generated (100% AI, 0% Human)
• 🛠️ Mostly AI-generated (AI draft, Human verified/modified)
• 👨‍💻 Mostly Human-written (Human lead, AI assisted or none)

🔗 Related Issue

📚 Technical Context (Skip for Docs)

• Reference URL: N/A
• Reasoning:
  • Integration Framework: As PicoClaw grows, relying solely on unit tests with mocks is no longer sufficient for testing complex network interactions or external dependencies. We needed a robust, generalized environment where we could spin up real services (via Docker Compose) and run Go tests against them seamlessly both locally and in CI.
  • MCP Transport: The previous transport logic was scattered, leading to confusion between standard SSE (which uses a standalone GET listener) and streamable HTTP. Standardizing the streamable-http alias and centralizing the parsing logic makes the codebase cleaner, the CLI more intuitive, and ensures maximum compatibility with different MCP server implementations.

🧪 Test Environment

• Hardware:
• OS:
• Model/Provider: N/A
• Channels: N/A

📸 Evidence (Optional)

Click to view Logs/Screenshots

The new integration framework automatically discovering and spinning up the mcp-streamable-server container, running the Go tests against it to verify the new transport logic, and gracefully tearing down.

☑️ Checklist

• My code/docs follow the style of this project.
• I have performed a self-review of my own changes.
• I have updated the documentation accordingly.