fix(cli): expanding an off-screen block triggers a full redraw that clears pre-Maka scrollback #1097

Problem

tui.setClearOnShrink(false) keeps the transcript shrink path from wiping terminal scrollback, but a documented known limit remains (pi-tui-runner.ts, "Known limit" comment): a global Ctrl+O / Ctrl+T toggle that resizes a block sitting above the live viewport top makes pi-tui's differential renderer fall back to a full redraw (its firstChanged < viewportTop path), which emits a scrollback-clearing sequence. Transcript content is rebuilt into fresh scrollback, so nothing is lost from the transcript itself — but the user's scroll position resets and any pre-Maka terminal scrollback is cleared.

Verified 2026-07-16 against main: the other half of the original #549 gate — 80×24 truncation semantics — is already satisfied by the #1082 compact-row grammar (assembleCompactToolRow preserves the tool head, truncates the free-text target first, and reserves protected fixed-shape annotations; the remaining unprotected-annotation gap is #1086).

Desired outcome

Expanding or collapsing blocks must never clear pre-Maka terminal scrollback or reset the user's scroll position. The clean fix is a preserve-scrollback render path inside pi-tui (upstream, not owned by this repo); evaluate an upstream patch against a maka-side avoidance strategy (e.g. anchoring expansion so resizes stay inside the live viewport). Add behavioral coverage for long runtime-resource paths and off-screen expansion.

(Split out of the retired #549 tracker.)