Preview MCP: launch.json runtimeArgs path ignored — server always serves Desktop directory

Bug Description

The Claude Preview MCP tool (preview_start) ignores the directory path specified in launch.json runtimeArgs and always serves from the user's Desktop directory instead.

Steps to Reproduce

1. Configure launch.json with a specific serve path:

{
  "version": "0.0.1",
  "configurations": [
    {
      "name": "ae-report-preview",
      "runtimeExecutable": "npx",
      "runtimeArgs": ["serve", "-l", "3456", "C:/Users/MarvinGuss/AppData/Local/Temp/pipeline-csvs"],
      "port": 3456
    }
  ]
}

1. Call preview_start with the configuration name
2. Take a screenshot or snapshot of the served page

Expected Behavior

The server should serve files from C:/Users/MarvinGuss/AppData/Local/Temp/pipeline-csvs as configured in runtimeArgs.

Actual Behavior

The server always shows "Index of Desktop/" — serving the user's Desktop directory regardless of the path configured in runtimeArgs.

Verification

Running the exact same command manually in the terminal works correctly:

cd "C:/Users/MarvinGuss/AppData/Local/Temp/pipeline-csvs"
npx serve -l 3457 .
# → correctly shows "Index of pipeline-csvs/"

This confirms the issue is in how preview_start spawns the process, not in npx serve itself. The tool appears to either:

• Drop the path argument from runtimeArgs, or
• Set the working directory to Desktop instead of respecting the configured path

Environment

• Platform: Windows 11 Pro 10.0.26200
• Claude Code Desktop App
• Shell: bash
• The issue persists across sessions and after killing stale processes on the port