SU.1209 CadCraft: draw.io XML to 2D geometry (DIAGRAM reads <mxfile> / <mxGraphModel>, positions kept)

Asked (#1209, Nov 5): turn the draw.io XML a local model (Qwen coder) writes into 2D geometry, so PDF/SVG content a model reads can become drawing objects; feed it straight from a local LLM.

Built in /lab: DIAGRAM (T2D), the diagram_from_text tool and its headless twin read draw.io XML: boxes, rounded, ellipse, rhombus, text, swimlane/container boxes (dashed, titled), connectors with waypoints, arrow ends, dashed; HTML labels to text; positions kept (12 px = the text height); draw.io's compressed save is inflated first. Local model: no new code, it already works through AC.7 (Ollama / LM Studio / llama.cpp recipes) calling diagram_from_text with format drawio; not tried with a real local runner (none installed). Untested on real draw.io files beyond the test fixtures; shapes of other kinds are drawn as boxes, images and loose-end connectors skipped and counted. Test: bin/test-cadcraft.mjs, 9 new checks.