fix(tui): keep raw output above composer in zellij

[fcoury-oai]

Why

Raw output mode intentionally sends logical source lines to the terminal without Codex-inserted wrapping so copied content retains its original line structure. In Zellij, soft-wrapped continuation rows from those raw lines are not confined by the inline history scroll region. When raw mode replays a long transcript, continuation rows can occupy the composer viewport and are overwritten on the following draw, leaving the transcript visibly truncated underneath the composer.

This is specific to the combination of Zellij and raw terminal-wrapped history. Rich output and non-Zellij terminals should continue using the existing insertion behavior.

Related context: #20819 introduced raw output mode, and #22214 removed the broad Zellij insertion workaround after the standard rich-output path no longer required it.

Before	After

What Changed

• Cache Zellij detection in Tui and select a dedicated insertion mode only for HistoryLineWrapPolicy::Terminal batches in Zellij.
• For that guarded path, clear the existing viewport, append raw source lines through the terminal so its soft wrapping remains selection-friendly, and reserve empty viewport rows before redrawing the composer.
• Add snapshot regressions for both an incremental soft-wrapped raw insert and an overflowing raw transcript replay that starts at the top of the cleared terminal.

How to Test

1. Start Codex inside Zellij with raw output enabled or toggle raw output after a multiline response is in history.
2. Produce or replay output containing long logical lines, such as a fenced shell command with several wrapped lines.
3. Confirm the wrapped history remains visible above the composer and the composer no longer overwrites the end of the response.
4. Toggle back to rich output or run outside Zellij and confirm standard history rendering still behaves normally.

Targeted tests run:

• just test -p codex-tui vt100_zellij_raw -- --nocapture

Additional validation notes:

• just test -p codex-tui was attempted; the two new Zellij raw insertion tests passed, while two existing app::tests::update_feature_flags_disabling_guardian_* tests failed outside this history insertion path.
• just argument-comment-lint was attempted but local Bazel analysis fails before reaching the changed source because the LLVM compiler-rt package is missing include/sanitizer/*.h. Modified literal callsites were inspected manually.

[canvrno-oai]

Note: When testing with zellij and raw output disabled, I did observe issues with text leaking into the composer (see screenshot). This also occurs on the current release of Codex, it is not a regression introduced by this branch.

[fcoury-oai]

Note: When testing with zellij and raw output disabled, I did observe issues with text leaking into the composer (see screenshot). This also occurs on the current release of Codex, it is not a regression introduced by this branch.

Can you check your zellij version with --version? It is expected to be broken if < 0.44.1.