feat(odf): draw the shape elements the parser used to drop

[andiwand]

🤖 Generated with Claude Code

Stage 2 of #771, on main now that #796 has landed.

parse_any_element_tree knew nine drawing tags; everything else fell through
its final return {null_element_id, …} and vanished with its subtree. This
maps the rest onto the types that already exist rather than inventing new ones,
the way draw:g already collapses onto frame:

tag	type	why
draw:path, draw:polygon, draw:polyline, draw:regular-polygon, draw:connector	custom_shape	geometry given as a path, which is what ODF's own term means
draw:ellipse, and a draw:circle/draw:ellipse draw:kind cuts	circle / custom_shape	the box, or the arc it traces
draw:measure	line	svg:x1/y1/x2/y2, same as draw:line
draw:caption	rect	the box; the callout tail is dropped
dr3d:scene	—	a 3-D scene is not a 2-D path

CustomShape::path() hands the renderer a DrawingPath — an svg d plus the
user-space box it is written in — and the renderer draws it into an
<svg viewBox> sized to the shape. odf_geometry.cpp builds one from svg:d,
draw:points, draw:corners or the arc draw:kind asks for. An svg:d is
parsed and re-serialised rather than forwarded, so nothing the file wrote
reaches the output as markup.

Notes

• A draw:connector carries svg:x1/y1/x2/y2 but no box, and a curve's
  control points can reach outside its endpoints, so its path is what places
  it; the svg:d is in the page's own coordinates at 1/100 mm. A straight one boxes
  to nothing in one axis, which svg refuses, hence the one-unit floor.
• An outline that never closes is drawn fill="none": svg would else fill it as
  if it did, and libreoffice draws an open draw:path as a line. 3 of the
  corpus's 6 draw:path are open; all 349 enhanced paths close.
• vector-effect="non-scaling-stroke" on the path: the view box scales, and
  with preserveAspectRatio="none" unevenly, which the stroke must not follow.
• Two fixes along the way: translate_circle wrote r="50%", a circle
  inscribed in the box rather than the ellipse ODF means, and text:measure
  had no parser, so a measure's label came out empty.
• New public DrawingPath and CustomShape::path(), mirrored in the JNI,
  Apple and Python bindings.

Verification

Five of the nine tags occur nowhere in the test corpus, so they are covered by
unit tests over string literals instead: odf_geometry_test.cpp.
SpotfaceCoord40270-L.odg was compared against libreoffice's own png export.

The reference-output pin is advanced: 17 files over 8 documents, every changed
line an insertion of a newly drawn shape or its label, bar the 26 <circle>
that become <ellipse>.