fix: align interactive mode authentication with exec mode

[inureyes]

Summary

• Fixed interactive mode connection failures when using cluster configurations with SSH keys
• Aligned authentication behavior between interactive and exec modes for consistency

Changes

• Added authentication parameters (key_path, use_agent, use_password, strict_mode) to InteractiveCommand struct
• Refactored determine_auth_method() in interactive mode to use the same logic as exec mode
• Updated CLI to pass authentication parameters from command-line arguments and config to interactive mode
• Updated all tests and examples to include the new authentication fields

Problem Solved

Previously, interactive mode ignored CLI authentication parameters and cluster SSH key configurations, causing connection failures when running commands like bssh -c orin interactive. The mode had its own simplified authentication logic that only checked for SSH agent and default key locations.

Now interactive mode respects:

• Cluster-specific SSH keys from config files
• CLI parameters like -i/--identity, --use-agent, --password
• The same authentication priority order as exec mode

Test Plan

• Code builds successfully with cargo build --all-targets
• All clippy warnings resolved
• Code formatted with cargo fmt
• Manual testing with cluster configurations
• Interactive mode connects successfully with SSH key authentication