Switch MCP server from stdio to SSE/Streamable HTTP transport

[apireno]

Problem

The current MCP server uses stdio transport, meaning it must be spawned as a child process by a single MCP client (e.g. Claude Desktop). This means:

• Only one client can use it at a time (Claude Desktop OR Claude CLI, not both)
• Server lifecycle is tied to whichever client spawned it
• Each client needs its own config entry

Solution

Switch to SSE (Server-Sent Events) or Streamable HTTP transport:

• MCP server runs as a standalone long-lived HTTP server on localhost:9876/mcp
• Any number of MCP clients connect via URL
• Server runs independently — start once, all clients share it
• The WebSocket bridge to the Chrome extension stays the same
• Claude Desktop config uses "url" instead of "command" + "args"

Implementation

1. Swap StdioServerTransport for StreamableHTTPServerTransport (or SSEServerTransport)
2. Add Express/Hono HTTP server to host the transport
3. Update Claude Desktop config format to URL-based
4. Add npx domshell serve entrypoint
5. Update README docs

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