UI.5 Arrange by dragging: move any block, palette or bar to another place and save it as your own layout

Owner: each layout can be customized, or a person creates their own. Today "Arrange your own layout" (WS.25, app-workspace-arrange.js) is a form: a dialog with radio buttons for where the toolbox goes, which panel holds which palette, which bars show; one palette stack, no split editors; a new layout is made from the form, not from the screen. Change: an Arrange mode (Settings › Layout › Arrange, or the grip's "…" › Arrange) that draws the slot map of UI.1 over the live page as drop targets and lets the person drag every block (ribbon, tool rows, menu bar, toolbox, palettes, info box, quick bar, view tabs, status bar, command line) by its grip to another allowed place, to float, or to a window (UI.3); blocks that cannot go there say so on hover (the format's places list is the rule); a palette may be dragged out of its stack into the other panel or into a stack of its own (two palette stacks: a format v2 change, UI.6). Done = the result saved as "My <layout name>" (file:my-<id>, the existing WS.17 path) and chosen; Reset puts the built-in back. Every drag is also an undoable step while the mode is on. Replaces the form, keeps its validation (validateLayout, resolveLayout). Test: a drag of each block kind in CadCraft and BimCraft, saved, reloaded, exported and imported again byte-identical. Owner addition the same day (UI.21): the drop targets are the dock zones of the one dock manager, so a ribbon group dragged to a side column becomes a palette there, a palette dragged to the top joins the ribbon, and either dropped on another unit joins it as a tab.