Harden hierarchical devtools chart routing

[SandroMaglione]

Summary

• Align hierarchy-crossing transitions with the vertical chart direction and preserve safe compound-header anchors.
• Keep deep parallel-owner routes local, label them inside the owning region, and reserve clearance around initial markers.
• Extend parent-origin cues and add deterministic regressions for compound returns, deep branch fan-out, child outcomes, and the parallel-owner visual example.

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

Type performance is not required because the change is internal to the devtools chart. The local runtime and memory smoke test completed successfully; CI provides the authoritative base-versus-PR comparison.