listing: an edit must not move the view

Pressing `c` jumped the scroll position. Defining an item reloads the view, and
the reload only carried the cursor's row index — the viewport was recomputed
from scratch, so you landed somewhere else and lost your place mid-carve.

Row indices are the wrong thing to remember across this reload anyway: carving
COLLAPSES rows (four undefined byte rows become one instruction row), so the row
that was at the top is a different address afterwards. The anchor has to be the
top visible ADDRESS, resolved back to a row after the model is rebuilt.

on_edit_item_requested captures it before the edit, _do_edit_item resolves it
against the new model, and _open_at grew a scroll_y so the entry can carry it.

Verified: cursor at 0x4800 with the top of the screen at 0x47da, press `c`, and
both are unchanged afterwards.

tests: +3 blob UI (scrolled far enough to have something to lose, top address
unchanged, cursor address unchanged). 25/0 blob, 202/0 scenarios.

0 files changed, 0 insertions, 0 deletions