Flat preference rows on the 0.2.x Plugins page + plugin icon

On 0.2.x hosts the config entry rendered a nested collapsible card inside the bundle detail section, whose chrome the manager already owns — this release renders the preference rows flat there and aligns the segmented controls with the platform selection idiom.

• Flat preference rows on the 0.2.x Plugins page: the seven preferences now render flat and always extended in the bundle detail section instead of inside a nested card. The rows and their settings wiring are shared with the 0.1.x card (PreferenceRows / usePreferenceState), so both seats stay in sync from one source.
• The new seat re-exposes the --did-* text and hover tokens from the label aliases. The rows only inherited them under .did-root/.did-card, so on the page every var(--did-text-*) was invalid at computed-value time and collapsed to the inherited near-white primary, flattening the secondary/muted hierarchy.
• Segmented controls follow the platform actionButton idiom: the selected segment carries the business accent as text color plus 600 weight with no backdrop box, focus-visible gets an explicit ring, and disabled segments dim instead of looking interactive.
• Plugin icon: a split add/del mark ships in the tarball and on the Plugins page.