Initial hybrid graph layout crate

README.md

@@ -0,0 +1,52 @@
+# epiphany-graph-rs
+
+Hybrid graph layout for DAGs that still want to breathe.
+
+This crate treats Sugiyama as a constraint generator instead of a final layout.
+The Sugiyama pass assigns ranks and same-rank order; the force pass relaxes
+those constraints with springs, repulsion, collision, and edge direction
+pressure.
+
+The result is a spectrum:
+
+- force-dominant for organic structure
+- Sugiyama-dominant for hierarchical DAGs
+- hybrid for the usual graph reality, where purity gets mugged in the hallway
+
+## Current Pipeline
+
+1. Assign ranks from directed edges using a longest-path DAG pass.
+2. Preserve partial hierarchy for cyclic leftovers with local edge pressure.
+3. Order nodes inside each rank with repeated barycenter sweeps.
+4. Generate rank, order, and edge-direction constraints.
+5. Relax the graph with deterministic force iterations.
+
+## Example
+
+```rust
+use epiphany_graph_rs::{layout, Graph, LayoutConfig};
+
+let mut graph = Graph::new();
+let a = graph.add_node(1.0);
+let b = graph.add_node(1.0);
+let c = graph.add_node(1.0);
+
+graph.add_edge(a, b);
+graph.add_edge(b, c);
+
+let result = layout(&graph, &LayoutConfig::default());
+
+for node in result.nodes {
+    println!("{:?}: ({}, {}) rank={}", node.id, node.x, node.y, node.rank);
+}
+```
+
+## Notes
+
+The first release favors a small deterministic core over a sprawling layout
+cathedral. The public API exposes generated constraints so callers can inspect,
+reuse, tune, or replace the force relaxation phase later.
+
+The current repulsion pass is exact pairwise repulsion. That is simple and
+stable for modest graphs; larger graphs should move toward a Barnes-Hut or grid
+approximation before pretending heroism is a scalability plan.