Align Copilot rate limit default to 5000

[ewega]

Summary

The CLI sends
ateLimitPerHour: 4500\ for all connections. The Copilot plugin's default is 5000 (\DefaultRateLimitPerHour\ in \models/connection.go).

Changes

• In \BuildCreateRequest\ and \BuildTestRequest, use 5000 for \gh-copilot\ plugin, keep 4500 for others

Acceptance Criteria

• Unit test verifies Copilot create request has rate limit 5000
• Unit test verifies GitHub create request still has rate limit 4500

[ewega]

Implemented in the enterprise support branch. Scope ID fix, connection testing, rate limit alignment, and Connection struct enrichment all shipped.