Refactor TUI input handling

[rosterloh]

Summary

• extract TUI key handling and action helpers into talos-tui/src/input.rs
• keep terminal setup, draw loop, polling, and teardown in talos-tui/src/main.rs
• move the topic toggle send-failure regression test onto the new input seam
• update CHANGELOG.md

Verification

• rtk cargo fmt --check
• rtk cargo test -p talos-tui --offline (with temporary rclrs_ws/install symlink to existing ROS install): 18 passed
• rtk cargo test -p talos-tui --locked: blocked before compile, missing rclrs_ws/install/action_msgs/share/action_msgs/rust in this worktree
• rtk cargo check -p talos-common -p talos-cli -p talos-tui --locked: blocked before compile, same missing generated ROS path