fix(ui): harden Rui across terminal sizes and shells

[EdgarSocrates98]

Rui terminal resilience

Harden the stdlib TUI copy used by api-forge for narrow and wide terminals, long menus, ANSI/ASCII rendering, POSIX EOF/CSI input, Windows key normalization, resize polling, empty navigation, and suspended actions.

Included

• responsive cell-bounded compositor and table allocation
• safe navigation at empty and long menus
• EOF/Ctrl-D and bounded key-sequence reads
• attached output for suspended actions
• accessibility and terminal compatibility documentation
• regression coverage for viewport, input, fallback, and lifecycle behavior

Verification

• $env:PYTHONPATH='src'; python -m pytest tests/test_ui_tui.py tests/test_ui_resilience.py -q
• python -m compileall -q package sources
• real external PTY/ConPTY validation remains documented as UNVERIFIED

No runtime dependencies or provider/install policies changed.