feat: add --config CLI for agent settings with provider-specific BYOK

[0xeb]

Summary

• Add --config [path] [value] CLI option to view/set agent configuration without entering interactive mode
• Support provider-specific BYOK paths: agent.byok.{claude,copilot}.{enabled,key,endpoint,model,type}

Examples

idasql --config                              # Show all settings
idasql --config agent.provider copilot       # Set provider
idasql --config agent.byok.copilot.model     # Get copilot model
idasql --config agent.byok.copilot.key "..." # Set copilot API key

Test plan

• idasql --config displays current settings (requires $IDASDK/src/bin in PATH)
• idasql --config agent.byok.copilot.model returns configured value