fix(tui): limit user shell output by screen lines

[muyuanjin]

What

• Limit the TUI "user shell" output panel by the number of visible screen lines rather than by the number of logical lines.
• Apply middle truncation after wrapping, so a few extremely long lines cannot expand into hundreds of visible lines.
• Add a regression test to guard this behavior.

Why
When the ExecCommandSource::UserShell tool returns a small number of very long logical lines, the TUI wraps those lines into many visual lines. The existing truncation logic applied USER_SHELL_TOOL_CALL_MAX_LINES to the number of logical lines before wrapping.

As a result, a command like:

• Ran bash -lc "grep -R --line-number 'maskAssetId' ."

or a synthetic command that prints a single ~50,000‑character line, can produce hundreds of screen lines and effectively flood the viewport. The intended middle truncation for user shell output does not take effect in this scenario.

How

• In codex-rs/tui/src/exec_cell/render.rs, change the ExecCell rendering path for ExecCommandSource::UserShell so that:
  • Each logical line from CommandOutput::aggregated_output is first wrapped via word_wrap_line into multiple screen lines using the appropriate RtOptions and width from the EXEC_DISPLAY_LAYOUT configuration.
  • truncate_lines_middle is then applied to the wrapped screen lines, with USER_SHELL_TOOL_CALL_MAX_LINES as the limit. This means the limit is enforced on visible screen lines, not logical lines.
  • The existing layout struct (ExecDisplayLayout) continues to provide output_max_lines, so user shell output is subject to both USER_SHELL_TOOL_CALL_MAX_LINES and the layout-specific output_max_lines constraint.
• Keep using USER_SHELL_TOOL_CALL_MAX_LINES as the cap, but interpret it as a per‑tool‑call limit on screen lines.
• Add a regression test user_shell_output_is_limited_by_screen_lines in codex-rs/tui/src/exec_cell/render.rs that:
  • Constructs two extremely long logical lines containing a short marker ("Z"), so each wrapped screen line still contains the marker.
  • Wraps them at a narrow width to generate many screen lines.
  • Asserts that the unbounded wrapped output would exceed USER_SHELL_TOOL_CALL_MAX_LINES screen lines.
  • Renders an ExecCell for ExecCommandSource::UserShell at the same width and counts rendered lines containing the marker.
  • Asserts output_screen_lines <= USER_SHELL_TOOL_CALL_MAX_LINES, guarding against regressions where truncation happens before wrapping.

This change keeps user shell output readable while ensuring it cannot flood the TUI, even when the tool emits a few extremely long lines.

Tests

• cargo test -p codex-tui

Issue

• Fixes TUI user shell output not limited when lines are extremely long #7447

[etraut-openai]

Thanks for the contribution!