[FEATURE] Cumulative dependency metrics (CCD/ACD/RACD/NCCD) + visibility metrics

[LukasNiessen]

In short

Extra whole-project 'how tangled is everything' scores (standard numbers like CCD/ACD you can trend over time), on top of the per-file metrics it already computes.

Problem

Cumulative dependency metrics summarize how entangled a whole component graph is in a single comparable number (and how far it is from an ideal balanced tree) — exactly what you want to trend and gate over time. The existing metrics are per-element; these are whole-graph.

Proposal

Add cumulative component-dependency metrics — CCD, ACD, RACD, NCCD — and per-component visibility metrics on the existing metrics(...) entry, e.g. metrics("src").cumulative().ccd().shouldBeBelow(...), alongside the existing coupling/abstractness/instability metrics and dashboards.

Acceptance criteria

• CCD/ACD/RACD/NCCD are computed for a selected component set and exported in the existing report formats.
• Values match the standard definitions on a known fixture.