docs: update README with STDIO transport configuration

[CalvinAllen]

Parent Epic

Part of #18 - STDIO Transport Support (Broker + Shim Architecture)

Description

Update documentation to explain the broker architecture, STDIO transport via the shim, multi-instance support, and configuration.

Implementation

Modify: README.md

New Sections

Broker Architecture

• How the broker manages multiple VS instances
• Auto-start: first VS instance spawns the broker, subsequent instances register
• Health checks and automatic cleanup

STDIO Transport (Claude Desktop/Code)

• Prerequisites: VS running with extension loaded
• Configuration:

{
  "mcpServers": {
    "visual-studio": {
      "command": "C:/path/to/CodingWithCalvin.MCPServer.Shim.exe",
      "args": ["--broker-port", "5100"]
    }
  }
}

• Finding Shim.exe path (VS extension install directory)
• How it works: Shim bridges STDIO to broker's HTTP endpoint

HTTP/SSE Transport (Direct)

• For custom MCP clients
• Connect to http://localhost:5100/sse

Multi-Instance Support

• Multiple VS instances auto-register with broker
• Instance discovery: list_instances tool
• Instance selection: select_instance tool
• Auto-matching by working directory

Configuration

• Broker settings: UseBroker (default: true), BrokerPort (default: 5100)
• Standalone mode: disable broker for single-instance simplicity

Comparison Table

	Standalone (No Broker)	Broker + HTTP	Broker + STDIO (Shim)
Best for	Single VS, simple setup	Custom MCP clients	Claude Desktop/Code
Multi-instance	No	Yes	Yes
Setup	Connect to localhost:5050/sse	Connect to localhost:5100/sse	Configure Shim.exe path
VS must be running	Yes	Yes	Yes

Dependencies

• Requires all other phases complete

Acceptance Criteria

• Broker architecture documented
• STDIO mode with Shim documented
• Claude Desktop/Code config examples included
• Multi-instance workflow documented
• Standalone vs broker mode comparison
• Prerequisites clearly stated
• Path finding instructions for Shim.exe