A behaviour suite for export and inspect, written from public documentation of design tools'
export settings and developer handoff modes (`crates/engine/src/export_behaviour_tests.rs`,
`crates/engine/src/inspect_behaviour_tests.rs`: 19 tests, 139 table rows and asserts, each with a
one-line derivation; rows where the docs are silent say so and pin today's behaviour). 47 cases
failed on `main`; this PR fixes them in shared code.
**Fixes**
- Export bounds are what a layer paints (`Document::world_render_bounds`, used by every export):
a drop shadow adds room only in the direction it falls (it was a symmetric margin of blur +
largest offset on every side); strokes on rectangles, frames and ellipses reach their real width
(the mitre factor made a centre stroke of 4 add 8 a side); hidden children take no room; a mask
group exports the mask's area.
- Slices export everything visible in their area (they exported an empty image).
- Slashes in layer names export into folders (`icons/close` → `icons/close.png`, folders created;
`.` and `..` segments dropped).
- Copy as PNG copies the whole selection (only the first layer was copied), now from shared code
(`cmd::file::copy_png`).
- Inspect positions are measured from the frame around a layer; groups aren't frames.
**Added (documented options that were missing)**
- Export settings: contents only (off draws every layer showing in the area) and include bounding
box (the layer's own box); SVG: outline text (off writes `<text>` with a `<tspan>` per line),
id attributes (unique), simplified strokes (stroke attributes for centred strokes, and for inside
and outside strokes on boxes and ellipses). Stored per export setting, taken by `file.export`,
`export.add` / `export.update`, `file.exportLayers` and MCP `export`; a "…" popover on each row of
the Export section.
- Inspect: colour formats hex / RGB / CSS / HSL / HSB (`inspect.properties {colorFormat}`, a Color
format dropdown), a Blend row, CSS in rem (`inspect.code {unit, rootFontSize}`, px/rem dropdown),
CSS for rotation, blend modes, gradient directions and kinds (linear angle, radial, conic), text
alignment, case and decoration; icons and images in the asset list (`kind`), exported with
`file.exportLayers {assets: true}`.
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