Feature/extension bar and explorer tooltip (#4489)

* feat(visualization): move file extension bar above bottom bar

The metric distribution strip is now fixed directly above the bottom
bar instead of sitting below the toolbar. It publishes its height as
--cc-file-extension-bar-height, which the floating metrics bar, the
legend, both sidebars, and the screenshot capture region account for.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* feat(visualization): add navbar dividers and link logo to codecharta.com

Separate Compare, 3D Print, and Settings with short vertical lines and
point the CodeCharta logo at https://codecharta.com/ instead of the
GitHub repository.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* feat(visualization): show building tooltip for explorer rows

Hovering a file or folder in the File Explorer shows the map's hover
tooltip (node name plus active area/height/color metric values),
anchored to the right edge of the hovered row. The tooltip service now
accepts a minimal TooltipNode so CodeMapNode works alongside the layout
Node. The native browser title tooltip on row names is removed as
redundant.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

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Co-authored-by: Christian Hühn <christian.huehn@maibornwolff.de>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>