forked from 1b-agent/opencadstudio-upstream
DIMTMOVE=1 ("moves the text and adds a leader") draws the leader from the midpoint
of the dimension line to the text, so a text dragged outside the dimension line gets
a diagonal that starts in the middle of the line and crosses the extension lines.
Mechanical-drawing practice (GB/T 4458.4, and what AutoCAD itself draws) extends the
dimension line along its own axis so that it runs underneath the text. Linear and
aligned dimensions now do that whenever the text is outside the dimension-line extent;
when the text is still inside it (only moved up/down) the previous connect-to-text
leader is kept. Every other dimension type is unchanged, and only dimensions with
DIMTMOVE=1 are affected at all (the shipped default is 0).
Adds four unit tests covering the placements (outside right, outside left, inside,
radius draws none) plus an integration render smoke test driven through the real
Scene::entity_wires() -> export_pdf() pipeline, gated by OCS_DIM_LEADER_PDF so CI
stays side-effect free.