[codex] refactor TUI to use native terminal scrollback

[lyfmt]

Problem

The TUI previously combined the transcript, streaming output, input, overlays, and status into an alternate-screen full-frame renderer. This hid terminal-native scrollback and text selection, imposed an application-managed history window, and made resize, close, and streaming updates prone to duplicated or transient lines entering history.

Root cause

Stable transcript content and mutable terminal chrome shared the same rendering lifecycle. The renderer could not distinguish append-only history from redrawable state, while alternate-screen and mouse-tracking modes transferred scroll ownership from the terminal to the application.

Changes

• Run the interactive TUI on the normal screen and return wheel, PageUp/PageDown, selection, and scrollback ownership to the terminal or tmux.
• Split the transcript into a stable prefix and live tail, then commit each stable block once per session projection through a dedicated ledger.
• Add cursor probing, inline viewport tracking, synchronized history insertion, and bounded mutable-surface diffing so streaming, input, overlays, and status remain redrawable without polluting scrollback.
• Preserve committed history across resize and close, restore terminal modes on shutdown, and keep the startup banner as a one-time native-scrollback prelude.
• Carry forward the prerequisite TUI reliability work for bounded tool progress, coalesced redraws, resume transcript projection, and provider fallback display.
• Replace alternate-screen history tests with unit, render-pipeline, boundary, performance, and real PTY/tmux coverage for the inline protocol.
• Update the project TUI skill with the new normal-screen invariants and regression entry points.

User impact

Long conversations remain available in terminal-native scrollback without a 500-line application cap. Streaming updates no longer leave intermediate copies behind, resize and exit preserve committed transcript, and standard terminal or tmux scrolling and selection work without TUI-specific history controls.

Validation

• mvn -pl lypi-transport-tui -am test
  • lypi-contracts: 140 tests passed
  • lypi-transport-tui: 400 tests passed
• Frame PTY coverage reached tui frame PTY passed before further smoke execution was stopped at user direction.