* fix(settings): preserve literal checkbox labels in KDE styles

KDE mnemonic processing consumed ampersands from escaped HTML entities, so provider names such as Research & Development <example> rendered as Research amp; Development lt;examplegt;. Supply mnemonic-safe text through Kirigami while preserving direct Qt label rendering.

Update usage and development guides, Unreleased, behavioral tests, and security wiring checks. TODO and catalogs are unaffected: no new CLI contract, setting, or translatable string.

* fix(ci): replace removed KDE neon image digest

The required check and smoke-runtime jobs fail before checkout because the registry returns manifest unknown for the previous digest. Resolve the official plasma:user image on 2026-09-12 and keep all three jobs pinned to its new digest.

Changelog records the contributor-visible CI fix. Existing setup instructions, configuration, catalogs, and TODO are unaffected.