[dweinstein]

What & why

Make the MCPB setup field explicit about the only two accepted product values:

• Enter platform for mobile apps the organization develops and scans.
• Enter mari for vendor and other third-party mobile apps.

MCPB 0.3 does not support enum/dropdown fields in user_config; adding an enum key causes Claude Desktop to reject the manifest. This keeps the supported string input while making the choice and accepted values unambiguous.

This also:

• Adds a manifest contract test that rejects unsupported product configuration keys and verifies the required/default value and server argument interpolation.
• Adds MCPB build guards that verify the macOS binary contains both arm64 and x86_64 slices and has a valid signature.
• Updates the README installation and build guidance.

Future dropdown work is tracked in #9 and is blocked by modelcontextprotocol/mcpb#165.

Validation performed:

• go test ./...
• Official mcpb validate
• make mcpb
• MCPB checksum and ZIP integrity verification
• Native arm64 launch on Apple Silicon
• Confirmed live Claude Desktop-launched nsmcp processes run as ARM64

Self-review

• Tests added/updated
• Ran it locally
• Reviewed own diff
• Edge cases considered