fix(cli): honor configured gateway port

[MicroMilo]

Summary

• use gateway.port from the loaded config snapshot when no CLI --port or PILOTDECK_GATEWAY_PORT is provided
• preserve existing precedence: CLI flag, environment variable, config, default 18789

Verification

• npm exec -- tsc --noEmit -p tsconfig.json

Notes

This is a real config/runtime mismatch: gateway.port was parsed into the config snapshot but the server startup path ignored it.