Add vector_legend() for svg/dxf legends (#103)

[MatthewDelprado]

Closes #103.

Adds vector_legend(file, position, size) — a chainable transformation that drops a vector file onto a cap the same way legend() drops text.

dcs_row(1) vector_legend("logo.svg", size=9) key();

How it works

Mirrors the text-legend path as closely as I could:

text	vector
legend() / front_legend() → $legends / $front_legends	vector_legend() / front_vector_legend() → $vector_legends / $front_vector_legends
keytext() (text() + linear_extrude)	keyimage() (import() + resize() + linear_extrude)

• keyimage() sits right next to keytext() in features/legends.scad; legends() loops the two new lists after the existing text loops.
• Honours $outset_legends / $inset_legend_depth and follows the dished top via top_of_key(), identical to text.
• size is the artwork width in mm; height keeps the file's aspect ratio. $vector_legend_fn sets import curve resolution.
• Inert by default — $vector_legends / $front_vector_legends default [], so len(...) > 0 skips the new blocks and plain keys render byte-identical.

Notes / things to decide

• Path resolution. import() runs from src/features/legends.scad, so it resolves paths relative to that dir, not the user's .scad. A bare filename next to the top-level file still works via OpenSCAD's document-root fallback but prints a DEPRECATED … found in document root notice. I've documented "use an absolute path" in the README, the example header, and the settings.scad comment, and the example acknowledges the notice. Open to a better approach if you have one.
• Naming. Went with vector_legend rather than svg_legend since import() takes DXF too (Picture-based legends? #103 asks for "picture" legends generally). keyimage() as the internal module name keeps the key* prefix.
• customizer.scad not regenerated. Matches the last legends change (Font can be explicitly set on a legend #173 / 7a5d2f0 touched only src/). expand.rb also currently needs ruby -E UTF-8:UTF-8 on a clean checkout, and a clean regen from master pulls in unrelated drift. This feature doesn't work in the Thingiverse customizer anyway (same as text $legends).
• Self-intersecting art. import() reads fills only, and a self-overlapping outline (traced logos, brush art) extrudes to a non-manifold cut — README notes the offset() roundtrip fix.

Example / testing

examples/vector_legend.scad covers inset, outset, text-stacking, DXF, and front_vector_legend(), using a hand-authored placeholder heart.svg / heart.dxf. Rendered on OpenSCAD 2026.06; SVG + DXF + front + regressions all check out.

🤖 Generated with Claude Code