Reject repeated fields in bundled MCP JSON #416

🤖 Generated by the Agentic Engineer

Problem

The package gate accepts a connection with repeated command fields, silently using one interpretation. Package validation should not choose between contradictory declarations on behalf of different clients.

Proposed direction

Require a single complete unambiguous MCP JSON object before semantic validation.

Acceptance criteria

• Reject repeated scalar and container fields and concatenated documents.
• Preserve distinct fields and valid server maps.
• Exercise duplicate declaration regressions at the package boundary.

Reproduced on current main before implementation. Rough size: S.