Open a design of another part: ask whether to start a new model

Opening (File > Open, a drop, the recent list) a design that has none of the
bodies the model's mesh and sets are on now asks, like the unsaved-changes
prompt: Start a new model with this design (default, Enter), Keep the
current model (the status names what no longer resolves), or Cancel. The
opened session waits for the answer; the same design opens without asking.
ui.inspect shows the prompt as {"design": path}; ui.prompt answers it.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo

docs/control-protocol.md

@@ -41,7 +41,7 @@ commands (files, undo, `model.info`) leave the ribbon where it is.
 
 | Method | Params | Notes |
 |---|---|---|
-| `ui.inspect` | — | view settings (`ui`), camera, viewport rect (points), renderer (`gpu`/`cpu`) and adapter, open command form, status bar, node and element counts, the results display (`results`: what the `results.*` commands reply: view, `stale`, contour range, modes), the probed node (`probe`), `busy` (the background job: a file opening, a solve, a mesher run from its form by a click on OK), `prompt` (`{"unsaved": path}`, `"recover"`, `"samples"`), `recent` (recent files), `selected` (the browser's selected definition), `nav` (the left-drag mode), `layout` (each region of the window drawn last frame as `[x, y, w, h]` in points: `app_bar`, `ribbon`, `workspace_switcher`, `document_tab`, `app_bar:<action>`, `browser`, `viewport`, `nav_bar`, `axis_view`, `selection_bar`, `context`, `command_line`, `timeline`, `toolbar_dropdown`, `palette`), version |
+| `ui.inspect` | — | view settings (`ui`), camera, viewport rect (points), renderer (`gpu`/`cpu`) and adapter, open command form, status bar, node and element counts, the results display (`results`: what the `results.*` commands reply: view, `stale`, contour range, modes), the probed node (`probe`), `busy` (the background job: a file opening, a solve, a mesher run from its form by a click on OK), `prompt` (`{"unsaved": path}`, `{"design": path}` (a design of another part opened over a meshed or defined model), `"recover"`, `"samples"`), `recent` (recent files), `selected` (the browser's selected definition), `nav` (the left-drag mode), `layout` (each region of the window drawn last frame as `[x, y, w, h]` in points: `app_bar`, `ribbon`, `workspace_switcher`, `document_tab`, `app_bar:<action>`, `browser`, `viewport`, `nav_bar`, `axis_view`, `selection_bar`, `context`, `command_line`, `timeline`, `toolbar_dropdown`, `palette`), version |
 | `ui.set` | any view setting: `style` (`shaded_edges`, `shaded`, `wireframe`), `show_nodes`, `show_geometry`, `show_mesh`, `show_loads` (boundary condition and load symbols), `show_interactions` (reference points, couplings, rigid walls), `perspective`, `dark`, `show_tree` (the browser), `show_timeline`, `workspace` (`prepare`, `model`, `analysis`, `results`), `tab` (the toolbar tab: `geometry`, `mesh`, `properties`, `assembly`, `steps`, `loads`, `interactions`, `solve`, `results`, `tools`; a tab of another workspace brings that workspace), `palette` (the command search open), `menu` (the open menu: `file`, `help`, `workspace`, `view`, `more`, or a panel's drop-down as `<tab>/<panel>` such as `mesh/Tet`; `null` closes it) | an unknown setting or value is an error; returns the settings |
 | `ui.view` | `view`: `front`, `back`, `left`, `right`, `top`, `bottom`, `iso`, `home` (iso and fit), `fit` | returns the camera |
 | `ui.camera` | `yaw`, `pitch` (degrees), `distance?` (model units) | turns the camera to any orientation about its target: `yaw` about Z (0 looks along +Y, the front view; −45 is the iso view's, −90 the right view's), `pitch` the elevation above the XY plane; `distance` moves the eye (the zoom of an orthographic view). Angles must be finite and the distance above 0: the yaw is wrapped, the pitch clamped to ±90 and the distance to 0.001–10⁹; anything else is an error. A sequence of calls orbits smoothly. Returns the camera (`ui.inspect`'s, angles in radians) |
@@ -50,7 +50,7 @@ commands (files, undo, `model.info`) leave the ribbon where it is.
 | `ui.select` | `kind` (`set`, `material`, `section`, `step`, `boundary_condition`, `load`, `reference_point`, `coupling`, `fluid_domain`), `name`; nothing to deselect | selects a definition as a browser click does; its properties (with Edit and Delete) show in the context panel |
 | `ui.select` (viewport) | any of `filter`, `box_mode`, `mode`, `clear`, `at`, `box`, `geometry`, `nodes`, `elements`, `faces` (and no `kind`) | changes the viewport's selection (see [Selection](#selection)); returns `ui.selection`'s reply |
 | `ui.selection` | — | the viewport's selection: `filter`, `box_mode` (box selection on), `count`, `capped`, `summary`, `items`, `params` (the selection as a set's members), `hover` (what a click would pick under the pointer) |
-| `ui.prompt` | `answer`: for `unsaved` `save`, `discard` or `cancel`; for `recover` `recover` (with `id` from `file.recovery.list`) or `close`; for `samples` `open` (with `name`) or `close` | answers the window's question (`ui.inspect`'s `prompt`) |
+| `ui.prompt` | `answer`: for `unsaved` `save`, `discard` or `cancel`; for `design` `new` (a new model with the design), `keep` (the design over the current model) or `cancel`; for `recover` `recover` (with `id` from `file.recovery.list`) or `close`; for `samples` `open` (with `name`) or `close` | answers the window's question (`ui.inspect`'s `prompt`) |
 | `ui.dialog` | `params?` (JSON object, fills the form), `use_selection?`, `run?`, `cancel?` | drives the open command form, in that order; `use_selection` is the form's Target row (see [Selection](#selection)); `run` returns the command's result and closes the form on success |
 | `ui.click` | `x`, `y` (screen points), `button?`: `left`/`right`/`middle`, `shift?`, `ctrl?`, `alt?`, `double?` | real pointer input; in the viewport a click selects what is under it (Shift adds, Ctrl/Cmd adds or removes, a click on nothing clears the selection), and a click on a results plot also probes the nearest node of the face under it (`solve.probe`; `ui.inspect` shows the values) |
 | `ui.move` | `x`, `y` | |