fix(tui): skip terminal probes in detached tmux

[cbusillo]

Summary

• skip startup terminal capability queries when running inside a detached tmux session
• keep attached terminals on the existing picker/font-size query path
• add parser coverage for tmux attachment output

Fixes #29.

Validation

• cargo test -p code-tui parse_tmux_session_attached_values
• cargo build -p code-cli
• detached tmux smoke: launched patched code in a detached session and confirmed it rendered/responded and created session files before attach
• ./build-fast.sh