refactor(ui): unify the Settings composition grammar

Sub-issue of #1303.

Problem

Settings already has the necessary low-level controls, but page composition is not governed. SettingsRows is only a wrapper and the current SettingRow covers only read-only values, so pages hand-build editable rows, section spacing, status clusters, expanded fields, and async states.

The result is observable drift:

• General places expanded proxy fields directly inside a grouped card.
• Memory places status and a switch as independent flex children.
• Open Gateway places a proxy grid outside the grouped-row surface.
• Daily Review and Data implement different label/control ordering.
• equivalent loading, failure, empty, pending, and read-only states use different treatments.

This issue owns the shared Settings composition seam. It does not redesign Settings navigation or module pages.

Already completed

• StatTile long-value containment — #1335
• DataTable wide-content containment — #1478

SettingsSection

• Own section heading, optional help, optional trailing action, and vertical spacing.
• Be unframed by default. Add a surface only when the contents form one grouped task.
• Do not repeat the page title or page description.
• Page code supplies content and data, not local padding, border, radius, or heading typography overrides.

ControlRow

Extend or rename the existing SettingsRows / SettingRow seam; do not leave a legacy editable-row path beside a new one.

• Own one label, optional description, one trailing control cluster, and optional status.
• Support horizontal and stacked layouts through one component-owned responsive rule.
• Keep control and status alignment inside one trailing cluster.
• Put conditional or full-width fields in an expanded-content slot or a separate section. Arbitrary grids, alerts, and action bars must not be direct children of the grouped-row container.
• Support read-only values, switches, selects, text fields, and row-scoped actions through the same label and description slots.
• Long labels, paths, identifiers, and localized values must wrap or truncate according to their semantics without horizontal page scroll.
• Static rows must not show hover feedback that implies the entire row is interactive.

Async states

• Keep the page header and stable section geometry while loading.
• Use a skeleton that resembles the eventual structure.
• Present failure as Alert with an inline retry action; failure is not an empty state.
• Use the shared EmptyState; add a compact variant only after at least two consumers demonstrate the need.
• Show pending state on the initiating control with aria-busy; disable only conflicting controls and keep layout stable.

Actions and confirmation

• One primary action per section.
• Row actions stay with the row; page-wide actions stay in the section footer.
• Reversible switches do not require confirmation.
• Destructive or irreversible actions use the governed confirmation dialog and name the affected object and consequence.
• Rare secondary actions may move to one overflow menu when they cannot fit at the supported narrow-window floor.

Reference consumers

The first migration must prove the grammar on:

• General proxy configuration;
• Memory status, preview, and maintenance actions;
• Open Gateway controls and proxy form;
• Daily Review settings;
• Web Search settings.

Page-group issues remain responsible for their page-specific hierarchy and content.

Acceptance

• Existing SettingsRows / SettingRow is extended or fully migrated; no parallel editable-row implementation remains.
• SettingsSection and the governed control row own their layout and responsive behavior.
• General, Memory, Open Gateway, Daily Review, and Web Search demonstrate the same grammar where semantics match.
• The 480px floor has no page-level horizontal scroll and no clipped control.
• Loading, error, empty, pending, long-label, and long-value variants are represented in stories.
• Responsive stacking, trailing alignment, static-vs-interactive feedback, and overflow are locked by focused contracts.
• Shared visual decisions live with the shared seam; page CSS retains page placement only.