Stagger a rectangular panel's new dashboard by rail order

Changing dashboard kept the grid mounted, so every new tile rose at once.
The grid is drawn afresh per dashboard and its tiles come in row by row:
from below, top row first, for one further down the rail, and from above,
bottom row first, for one further up, as a round panel's dashboards slide.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WgBfkm4rCmtd1T4vHWjEPx

docs/interface/dashboards.md

@@ -347,7 +347,7 @@ dashboard's look's.
 | Value face, Value and Gauge tiles | the number | counts to the new value, written to its precision | spring | retargets |
 | Slider tile set elsewhere | the fill's end, the handle, the reading's dot | from where it is drawn to the new fraction | spring | a drag or a key moves it at once |
 | Gauge and Bar tiles | the value arc, each bar's fill | from where it is drawn to the new fraction | spring | retargets |
-| Dashboard change (rectangular panel) | every tile | the old dashboard goes at once; each new tile opacity 0 → 1, y +8 → 0 | spring | — |
+| Dashboard change (rectangular panel) | every tile | the old dashboard goes at once. The new tiles come in row by row, 30 ms apart, each opacity 0 → 1 and y +8 → 0 (Glass: +12, and scale 0.96 → 1): from below, top row first, for a dashboard further down the rail, and from above (y −8 → 0), bottom row first, for one further up | spring | — |
 | Rail | the current entry's marker | slides to the new entry | spring | retargets |
 
 With reduced motion asked for, nothing travels on its own: a page under the