send_to_intruder corrupts HTTP requests by appending headers after body separator

[godoppl]

When using send_to_intruder, the tool injects additional headers (Connection: keep-alive and a duplicate Host header) after the blank line that separates headers from body, resulting in malformed HTTP requests that return 400 Bad Request.

Environment:

• Burp Suite Professional v2025.12.3
• MCP Server extension (latest from BApp Store)

Steps to Reproduce:

1. Use MCP client to call send_to_intruder with a valid HTTP request:

  POST /login2 HTTP/1.1
  Host: example.web-security-academy.net
  Cookie: verify=carlos; session=xxx
  Content-Type: application/x-www-form-urlencoded
  Content-Length: 13

  mfa-code=0000

2. Open the created Intruder tab (looks correct here)
3. Start the intruder attack

Expected Result:
Requests maintains proper HTTP format with headers, blank line, then body.

Actual Result:

  POST /login2 HTTP/1.1
  Host: example.web-security-academy.net
  Cookie: verify=carlos; session=xxx
  Content-Type: application/x-www-form-urlencoded
  Content-Length: 13
                                ← blank line
  Connection: keep-alive        ← INJECTED AFTER SEPARATOR
  Host: example...              ← DUPLICATE HOST HEADER

  mfa-code=0000

Impact:
All Intruder attacks using requests created via MCP return 400 Bad Request, making the send_to_intruder tool unusable.

Note: create_repeater_tab does NOT have this issue - only send_to_intruder is affected.