Stabilize devtools chart routing

[SandroMaglione]

Summary

• route every chart transition class through one deterministic ELK layout pipeline
• validate node, label, containment, overlap, terminal, and self-loop clearance invariants before rendering, with progressively more spacious fallbacks
• clarify parent-to-child transitions and add a hierarchy-routing stress example plus deterministic topology-corpus coverage

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 benchmark completed successfully. The change is isolated to the devtools renderer, so public type-performance measurement is not required.