[trailcode]

Note

Medium Risk
New duplication paths touch Design geometry, Workbench links, selection, undo, and mode switching; the hotkey and sequential naming changes affect everyday editing workflows.

Overview
Adds in-place duplicate for Design and Workbench (Shift+D, edit.duplicate): Design deep-copies selected solids (or the current group subtree); Workbench adds another link to the same body at the same pose. Copies stay under the original parent, get uniquified names, select the new nodes, enter Move, and record one Shape_add_delta undo step without touching the copy/paste clipboard. Active move/rotate/scale/align previews are cancelled first; Sketch rejects the action.

Remappable Delete now defaults to Ctrl+D so Shift+D can be Duplicate; Delete / Backspace still always delete. Settings defaults and user docs reflect edit.duplicate and the new Delete chord.

Copy naming fixes unique_sequential_name so a trailing .NNN is a sequence suffix (Box.001 → next free Box / Box.002, not Box.001.001).

Also documents and optionally lint-checks a C++ style rule: fold for/while bodies that are only a declaration plus an if into an if-with-initializer, with matching refactors across the view/shape/sketch code and new Shp_test coverage for duplicate and naming.

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