Inline writable numerics in device settings — match iOS Settings idiom

[tashda]

Problem

The state/action card surfaces a lot of value for fans, but the per-feature settings underneath it currently render writable numerics as a row that pushes a separate NumericDetailView containing only a slider. Tapping a "Speed", "Timer", etc. row to land on a near-empty page just to drag a slider is clunky — and inconsistent with how iOS Settings exposes numerics (Display & Brightness, Accessibility → Display & Text Size, etc., where sliders sit inline within the same grouped section).

The card itself is good and is out of scope — only the settings sections under the card need to change.

Goal

Make the settings sections under the fan card look and behave like native iOS Settings:

• Toggles inline (already done).
• Pickers/enums use the native Picker (already done).
• Writable numerics render the slider inline within the same List row — label + current value on top, slider beneath — instead of pushing a detail screen.
• Read-only numerics keep showing label + value as a plain row.
• Indexed groups (e.g. gradient_scene_*) keep their current "drill-in" affordance — those genuinely need their own page.

Scope

Start with fans. Once it looks right and tests pass, we'll roll the same pattern to lights / covers / climate / generic exposes in a follow-up.

Acceptance criteria

• A writable numeric setting under the fan card (e.g. replace_filter_age minutes, schedule timers) shows label + value + slider inline; tapping the row does not push a new screen.
• Read-only numerics still display label + value, no chevron, no push.
• Toggles and enum pickers are unchanged.
• The hero card and filter card are untouched.
• Tests cover: writable numeric renders an inline Slider; row does not behave as a NavigationLink.