feature: Phase 22 SEO metadata component for public site

One presentational SeoHead renders the full OG/Twitter/JSON-LD head surface at prerender via typed schema.org builders. Per-medium release schema, config-sourced canonicals, 404 noindex. Zero CMS change.

DeepDrftPublic.Client/Pages/SessionDetail.razor

@@ -3,8 +3,7 @@
 @using DeepDrftPublic.Client.Controls
 @using DeepDrftPublic.Client.Services
 @inherits ReleaseDetailBase
-
-<PageTitle>@(ViewModel.Release?.Title ?? "Session") - DeepDrft</PageTitle>
+@inject SeoOptions Seo
 
 @if (ViewModel.IsLoading)
 {
@@ -40,6 +39,10 @@ else
     // Hero image precedence: the session's dedicated hero, then the release cover, then a placeholder.
     var heroImage = !string.IsNullOrEmpty(heroKey) ? heroKey : release.ImagePath;
 
+    @* SEO head — fed from the same bridged release, so prerender and WASM render identical tags (AC6).
+       MusicAlbum/LiveAlbum (a session is a live release, §3.4/OQ6). *@
+    <SeoHead Model="@SeoModel.ForRelease(Seo, release)" />
+
     @* Ambient living waveform behind the hero overlay (Phase 12 §3e option b / §3f mode B). Session does
        NOT compose ReleaseDetailScaffold, so it mounts the shared engine directly with its own thin
        full-bleed wrapper — the engine is single-source either way, only the mount differs (§3b). The