fix(mcp): explicit JSONResponse on Windows reconnect (#4533)

[Elshayib]

Summary

Return JSONResponse from MCP server reconnect so h11 Content-Length matches the body on native Windows installs.

Target branch

• This PR targets dev, not main. All PRs land in dev; main is curated by the maintainer at each release. If your PR is on main by accident, click "Edit" on this PR and change the base.

Linked Issue

Fixes #4533

Type of Change

• Bug fix (non-breaking — fixes a confirmed issue)

Checklist

• I searched open issues and open PRs — this is not a duplicate.
• This PR targets dev
• My changes are limited to the scope described above — no unrelated refactors or whitespace changes mixed in.
• Verified with targeted pytest / syntax checks.

How to Test

1. On Windows native Odysseus add a stdio MCP server. 2. Click Reconnect in Settings. 3. No h11 LocalProtocolError in server log; status JSON returns.