mcp: select and selection tools for the app's viewport selection

Bridged to a running app, select and selection call ui.select and
ui.selection; headless they are errors (selection belongs to the
window).

Closes #73

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

docs/mcp.md

@@ -105,6 +105,8 @@ software on the computer.
 | `probe` | `step?`, `nodes?`, `elements?`, `points?`, `forces?`, `mode?`, `frame?` | `solve.probe`: stored results at nodes, elements (explicit) or points (fluid). |
 | `reactions` | `step?`, `sets?`, `about?` | `results.reactions`: reaction force and moment per node set and in total. |
 | `screenshot` | `view?`, `camera?`, `source?` (window, model), `width?`, `height?`, `path?` | A PNG image content block and what it shows. Headless: a CPU render framing the model, the geometry, the analysis setup's symbols (boundary conditions, loads, reference points, couplings; `sampled_symbols` lists definitions drawn with a sample) and the results display (deformed shape, contour bands). Bridged: the whole app window drawn offscreen (`ui.capture`, the default) or a model render with the app's camera (`ui.render`). `view` turns the camera to a standard view first; `camera` `{yaw, pitch, distance?}` to any orientation, in degrees (yaw 0 looks along +Y, −45 is the iso view's; pitch is the elevation, clamped to ±90) and model units (`ui.camera`; headless, the picture is framed unless `distance` is given). Give one of the two; the orientation is kept for the next picture, so a sequence of `camera` angles orbits smoothly. |
+| `select` | `filter?`, `box_mode?`, `mode?`, `clear?`, `geometry?`, `nodes?`, `elements?`, `faces?`, `at?`, `box?` | Bridged only: changes the app's viewport selection (`ui.select`; control-protocol.md, Selection) and returns it. Headless it is an error: selection belongs to the window. |
+| `selection` | — | Bridged only: the viewport selection (`ui.selection`), with `params`, the selection as a set's members for `model.set.create`. |
 | `undo`, `redo` | — | `edit.undo`, `edit.redo`. |
 
 Resources: `fieldcraft://model` (`model.info`) and `fieldcraft://commands` (the command catalog).