Fix duplicate /review messages in app-server TUI

[etraut-openai]

Symptoms

When /review ran through tui_app_server, the TUI could show duplicate review content:

• the >> Code review started: ... << banner appeared twice
• the final review body could also appear twice

Problem

tui_app_server was treating review lifecycle items as renderable content on more than one delivery path.

Specifically:

• EnteredReviewMode was rendered both when the item started and again when it completed
• ExitedReviewMode rendered the review text itself, even though the same review text was also delivered later as the assistant message item

That meant the same logical review event was committed into history multiple times.

Solution

Make review lifecycle items control state transitions only once, and keep the final review body sourced from the assistant message item:

• render the review-start banner from the live ItemStarted path, while still allowing replay to restore it once
• treat ExitedReviewMode as a mode-exit/finish-banner event instead of rendering the review body from it
• preserve the existing assistant-message rendering path as the single source of final review text

[etraut-openai]

@codex review

[chatgpt-codex-connector]

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