Removed outdated OpenCode Go first-month discount messaging and pricing

Fixes

• CoreFixed OpenCode device login links when servers return relative verification URLs or use a base path.
• CoreFixed textVerbosity being sent to OpenAI-compatible providers that do not support it.@joelstucki-taulia
• CoreUpdated the Amazon Bedrock provider for compatibility fixes.
• DesktopKeep model provider headers visible while scrolling the model picker.