* fix(overview): preserve providers with supplemental usage

The error-only predicate omitted normalized provider details and dashboard summaries, hiding useful snapshots from Overview and automatic selection. Include both fields and cover useful and malformed supplemental data after normalization and cache reconciliation.

Documentation: update usage and development guides plus the Unreleased changelog; TODO parity scope is unchanged. Validation: make check passed with documented local KDE skips; targeted QtTests and isolated Plasma before/after captures passed. Grok 4.7 high review found no actionable issues.

* fix(overview): require visible content in detail sections

An empty normalized chart container made an otherwise error-only provider eligible for Overview and automatic selection. Require a visible section or chart label, detail row, or valid chart point while preserving labeled empty charts.

Add regression cases that failed for empty and fully malformed chart points, plus positive section-title and chart-label cases. Update the usage/development guides and Unreleased changelog; TODO parity scope is unchanged. Validation: 39 Overview QtTests pass, make check passes with the existing local KDE skips and partial type metadata, isolated Plasma captures pass, and a second Grok 4.7 high review found no actionable findings.