* claim: #1801
* Insert SVG: the file picker opens on SVG files (#1801)
Every Open went through one host picker whose filters start with designs, CAD
files and meshes, so Insert SVG (and Insert DXF) in a sketch opened on STEP,
IGES and meshes, and the SVG file had to be found under another filter.
The host's pick_open now takes the extensions the command reads and offers
them as the picker's first, default filter. Insert SVG and Insert DXF pass
their type; every other Open passes none and keeps the list it had. The
browser host ignores them (it shows its own file panel).
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Co-authored-by: MateuszSychXpl <151755914+MateuszSychXpl@users.noreply.github.com>
One docked Save as mesh dialog replaces Export STL / 3MF / 3MF with face tags, with an optional Send to slicer that lists the slicers installed on this machine. Engine: file.save_mesh and file.slicers; the Convert Mesh dialog goes (mesh.convert and the MeshConvert feature stay, so existing designs open). Strings in all catalogs; screenshots in the PR. Checked on main + this branch: cargo check --workspace, the engine slicer/mesh/file tests, the UI catalog and menu tests and scenario s14 (the one local colour-token failure is epaint's TexturesDelta panic, which main shows on this machine too).
Open and Save use parented AsyncFileDialog sheets; their answers run on the UI thread in a later frame, so resizing the window while a picker is open no longer re-enters winit and aborts. Editors, tab changes, Close/Quit and model-changing control requests wait for the answer; the local library Open and Export in the Appearance dialog use the same flow. Fixes#1088.
