feature: Phase 18.6 Track A — public Settings menu + streaming-quality toggle

DeepDrftPublic.Client/Common/PublicSiteSettings.cs

@@ -0,0 +1,29 @@
+using Microsoft.AspNetCore.Components;
+
+namespace DeepDrftPublic.Client.Common;
+
+/// <summary>
+/// The single public-site listener-settings object (Phase 18 wave 18.6, §4a). The generalized analogue of
+/// <see cref="DarkModeSettings"/>: one scoped holder for every remembered listener preference, seeded at
+/// server prerender, carried into WASM via <see cref="PersistentState"/>, and persisted to a cookie on
+/// change. Today it carries one preference — streaming quality; tomorrow dark mode (and whatever follows)
+/// folds in here as another property without disturbing the menu that reads it.
+/// <para>
+/// Built design-for-adaptability per §4a: a new preference is a new <c>[PersistentState]</c> property here
+/// plus a new <see cref="Components.SettingsItem"/> in the menu — not a rewire. Dark mode is intentionally
+/// <em>not</em> migrated in now (it keeps its own <see cref="DarkModeSettings"/> seam); this object is shaped
+/// so that consolidation is later a merge of two identical seams, not a reconciliation of two different ones.
+/// </para>
+/// </summary>
+public class PublicSiteSettings
+{
+    /// <summary>
+    /// The listener's streaming-quality preference. Defaults to <see cref="StreamQuality.LowData"/> (Opus,
+    /// capability-gated — OQ2). Seeded from the <c>streamQuality</c> cookie at prerender; persisted on change
+    /// by the client cookie service. The player reads this to decide which <c>?format=</c> to request, but
+    /// the capability gate and C2 fallback still apply on top, so a <see cref="StreamQuality.LowData"/>
+    /// preference never forces an unplayable stream.
+    /// </summary>
+    [PersistentState]
+    public StreamQuality StreamQuality { get; set; } = StreamQuality.LowData;
+}