Fix WebSocket spacing and Ctrl-C shutdown behavior

[ryanfowler]

Summary

• Remove the extra spacer row after interactive WebSocket messages so wrapping and scrolling stay consistent.
• Reserve a blank line above the status/input area for clearer separation in interactive mode.
• Treat Ctrl-C as a successful exit instead of a runtime error, including WebSocket non-interactive mode.
• Add regression coverage for the updated interactive layout and Ctrl-C behavior.

Testing

• cargo fmt --check
• cargo clippy --locked --all-targets --all-features -- -D warnings
• cargo test --locked --all-features --lib --bins
• cargo test --locked --all-features --test websocket -- --test-threads=1
• Focused unit and integration tests for WebSocket interactive rendering and Ctrl-C handling passed.