Preflight terminal size gating does not trigger resize warning

Problem

The preflight UI no longer shows the "terminal too small" warning panel when the terminal window is too narrow for the rendered content. The UI renders with broken layout / wrapping instead of blocking and asking the operator to resize.

Where the check lives

• _terminal_size_ok() at preflight_ui.py:622 checks against MIN_UI_WIDTH = 132 and MIN_UI_HEIGHT = 34
• _wait_for_terminal_size() at preflight_ui.py:632 shows the resize panel in a loop until the terminal is large enough
• Called from _arrow_select() at preflight_ui.py:1400 on every menu render cycle

Likely causes to investigate

1. The fixed thresholds (MIN_UI_WIDTH = 132) may no longer match the actual rendered width of the preflight dashboard content, especially after recent UI changes added wider rows (session summary sections, launch contract, stim config view).
2. The check only runs inside _arrow_select — if the arrow select path is skipped (e.g., _supports_arrow_select() returns false), the numbered-menu fallback has no size check at all.
3. Rich may be auto-wrapping content to fit the terminal width, so the check passes but the layout breaks silently.

Expected behavior

When the terminal is too narrow for the preflight UI content, the resize warning panel should appear and block until the operator enlarges the window.

Observed on

Windows, native cmd.exe. Noticed 2026-04-15 after recent preflight UI changes.

Start in preflight_ui.py at _terminal_size_ok() and _wait_for_terminal_size(), then trace both the _arrow_select() path and the numbered-menu fallback. Compare the thresholds with the rendered preflight content and check whether Rich wrapping or skipped gating explains the behavior. Done means an undersized Windows cmd.exe terminal shows the resize warning and blocks until it is enlarged.