[bmc08gt]

Jumping to a message far up a transcript stopped several messages short of it. flipcash://chat/12e1d342-…/m/109 in a photo-heavy group landed on a post from the next morning instead of the 1:39 PM photo it names. It affects deep links, quote taps and boost detail's View Message, since they all end in ChatViewController.scrollToRow.

scrollToRow called scrollToItem(at:at: .centeredVertically) once. The offset came from ChatLayout's 56pt estimate for every row that had never been on screen, and nothing re-anchored after those rows self-sized. With photos several times that height, the target ended up above the visible area. scrollToBottom and scrollToRowTop already re-anchor through a position snapshot on the next runloop turn; the jump had no such pass.

Changes, all in ChatViewController:

• centerRow(at:) centres a row with a ChatLayoutPositionSnapshot worked out from the row's current height, top-aligning a row taller than the screen.
• The non-animated jump (a row that arrives with a loaded page) centres, flashes, and re-anchors once more on the next turn.
• The animated jump settles the destination first by centring twice, restores the reader's position from a bottom snapshot, then animates to the measured offset and re-anchors when it lands. All of the measuring runs before the next frame, so none of it is drawn.

scrollToMessage_tallRows_landsCentred(animated:) drives a windowed transcript of rows several times the estimate. Before the fix, the animated jump left the target 239pt above centre and the deferred jump left it off screen. Both cases now pass, along with the rest of ChatViewControllerTests and ChatReplyReturnTests.