Generate a small wire-raster thumbnail when saving a DWG and embed it via
acadrust's preview API, so OCS drawings show a thumbnail in file browsers
and other CAD applications. Read the embedded preview back cheaply (file
header + preview bytes only, no full parse) to show a thumbnail per file
in the Start page's Recent Documents panel.
- io/thumbnail.rs: CPU rasterizer (current-layout wires -> BMP DIB) plus
a preview-only reader/decoder (BMP/PNG -> iced handle) for the Start
page.
- Embedded on save via stamp_thumbnail on both save paths.
- recent_thumbs cache filled on config load / recents change (never from
a view); a thumbnail is drawn beside each recent file.
Requires acadrust at 3111694 (preview read/write), already pinned in
Cargo.lock.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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