Unwrap update-a-block payload before forwarding

[ayyYoSam]

Description

Fixes #342.

This updates the HTTP client to unwrap the type payload for the update-a-block operation before forwarding the request to the Notion API.

The Notion API expects block-type properties (such as paragraph and to_do) at the root of the request body, while the current MCP request shape nests them under type. The proxy now preserves the existing tool interface while sending the API-compatible request body.

Screenshot With Test

Commands:

$env:NODE_ENV="test"; npx vitest run
npx tsc --noEmit
npx prettier --write src/openapi-mcp-server/client/http-client.ts