feat(tui): improve active-turn controls and interaction polish

[danielsuit]

Summary

• make Esc stop an active turn and preserve queued follow-ups
• let Tab queue the current draft while a turn is running
• let Esc with a queued message hand off after the current tool batch; a second Esc stops immediately
• make in-app copy prefer native clipboards and tmux bridging, with OSC 52 as the remote fallback
• simplify turn dividers to elapsed time plus optional +N -N file stats
• surface queue state in the status bar and document the controls

Validation

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo test --workspace
• cargo test -p rc-tui after copy/divider changes

EC2 audit

The deployed checkout was inspected read-only. It is a stale dirty pre-release worktree; its only remote-only paths are retired planning notes and Harbor build artifacts, with no remote-only production source files to recover.