Fix complex statechart layout

[SandroMaglione]

Summary

• keep complex compound statecharts layoutable by routing self-transitions locally and retrying ELK with relaxed port constraints
• separate converging terminal lanes and self-loop labels so arrows and labels remain readable
• upgrade ELK to 0.12.0 and add an auth-shaped regression example covering nested updates and cross-hierarchy invoke outcomes

Changeset

• Added or updated for a library or package-metadata change
• Not required because this PR does not change a publishable package

Validation

• pnpm check
• Automated type-performance measurement passed or was not required
• Automated runtime- and memory-performance measurement passed or was not required

Local pnpm perf:runtime smoke test passed. The change does not affect the public TypeScript API, so a local type-performance run was not required.