fix(intent): lay out generated BPMN/EDM diagrams so they read cleanly

[iliyan-velichkov]

Problem

The intent generators emit diagram interchange — bpmndi:BPMNDiagram for .bpmn, mxGraphModel for .edm — because the Flowable/Oryx and EDM modelers render the canvas only from that block. Placement was naive, so generated files opened badly formatted and had to be reordered by hand:

• BPMN laid every node on a single line at X = declaration-index × spacing, with only two fixed Y lanes (main 140, else-branch 300). Parallel branches didn't align, multiple/nested decisions piled onto the same lanes and overlapped, and edges were straight diagonals cutting across other shapes.
• EDM used a blind index % 3 grid that ignored card heights (columns became wildly unequal) and the relation graph (FK-linked entities landed far apart, so connectors crisscrossed).

Change

BPMN — BpmnIntentGenerator: replace the single-line placement with a deterministic layered (Sugiyama-style) layout:

• Column (X) = longest-path distance from the start event (rankByLongestPath, cycle-guarded, end pinned rightmost), so a gateway's then/else branches share a column and the flow reads left-to-right.
• Lane (Y) = per-column assignment by the barycentre of each node's predecessors, spread symmetrically around a centre lane — branches fan out above/below instead of piling onto two fixed lanes.
• Edges routed orthogonally (right-angle L/Z) across lanes, straight when aligned.
• The obsolete secondaryBranchTargets single-drop heuristic is removed.

EDM — EdmIntentGenerator.appendMxGraphModel: place entities in a relationship-aware order (BFS over the FK graph so connected entities cluster) and pack each into the currently shortest column instead of index % 3, keeping columns balanced and related entities adjacent. Cells are still emitted in declaration order, so regeneration diffs stay stable.

Determinism & tests

Both layouts are pure functions of the model → output stays byte-stable; the modeler re-routes on first manual edit. Existing engine-intent unit tests and the IntentEngineIT / IntentEmissionCoverageIT assertions key on element/flow presence, not coordinates, so they are unaffected. All engine-intent unit tests pass locally; verified visually in a running instance against branching processes and multi-entity models.

🤖 Generated with Claude Code