Artboard tool: Alt-drag duplicates the artboard (and its art)

[theironchef]

Fixes #346.

Problem: with the Artboard tool, Alt-dragging an artboard moved it like a plain drag. In Illustrator it duplicates the artboard: the copy follows the pointer and, with Move/Copy Artwork on, carries copies of its artwork (Duplicate artboards). artboard.duplicate exists but always puts the copy right of the last artboard, without art.

Change

• artboard.move (engine, cmd/xform.rs) takes copy?: bool.
  • With it, the artboard and the art it carries stay put. A copy of the artboard, with a new id and named " copy", is moved by dx/dy, along with copies of that art.
  • Each art copy is re-numbered (Document::reid) and inserted just above its original.
  • The step is labelled "Duplicate Artboard", and the result's index is the copy's.
  • Without copy, nothing changes.
• The Artboard tool (tools/src/xform/artboard.rs) sends copy while Alt is held during a move drag. The step begins as "Duplicate Artboard" or "Move Artboard".
  • Alt pressed or released mid-drag cancels the step and begins the other one, as Free Transform does since Free Transform: a handle drag follows the modifiers held during the drag #269, so History names what happened.
  • On release, the copy becomes the active artboard.
• The params doc and the tool's module doc say so.

Tests

• New engine test artboard_alt_drag_duplicates_it_with_its_art, an Alt-drag through Session::pointer with the Artboard tool:
  • the result is two artboards: the original unmoved, and "Artboard 1 copy" 900 pt right with a new id;
  • the rectangle stays, and its copy sits 900 pt right;
  • History says "Duplicate Artboard", and one Undo removes both copies.
• It fails with the old tool (one artboard).
• New tool test alt_drag_moves_a_copy_of_the_artboard: the preview's copy flag and the Cancel/Begin switch when Alt changes mid-drag.
• The existing move_resize_create_delete now expects "copy": false in the move preview.
• cargo test -p vectorcraft-tools (189) and -p vectorcraft-engine (1254 and the integration tests, command sweep included): all passed.
• cargo clippy -p vectorcraft-tools -p vectorcraft-engine --all-targets -- -D warnings (Rust 1.99): clean.
• cargo fmt --all -- --check: clean.
• Checked by hand in a release build on Windows with real mouse and keyboard input:
  • in a 200 × 150 pt document with a rectangle, I Alt-dragged the artboard 220 pt right with the Artboard tool;
  • the result is "Artboard 1" still at x = 0 with its rectangle, plus "Artboard 1 copy" at x = 220 with a copy of the rectangle (x = 270);
  • History says "Duplicate Artboard", and the copy is the active artboard.

I didn't run the full cargo xtask ci (wasm step) here.

🤖 Generated with Claude Code

[bflatastic]

Thanks @theironchef, merged! Alt-drag with the Artboard tool now duplicates the artboard, with its art when Move/Copy Artwork with Artboard is on, and Alt pressed or released mid-drag switches between copy and move. I rebased it on main and added one commit on top:

• artboard.move {copy} and artboard.duplicate now share one copy helper.
• Over MCP I found that two copies of the same artboard were both named "Artboard 1 copy". They're now "copy", "copy 2" and so on.
• moved reports the copies' ids rather than the originals'.
• An engine test, and updates to the params doc and the ROADMAP.

Live check: an Alt-drag made "Artboard 1 copy" with its 6 objects copied, and one undo removed both. Releasing Alt mid-drag gave a plain move. Over MCP, artboard.move {copy, moveArt} returned {index: 1, moved: [7]}.