Phase 9 Wave 1: add ReleaseMedium discriminator + Session/Mix metadata

Add ReleaseMedium enum (Cut/Session/Mix) and two 1:1 satellite entities
(SessionMetadata, MixMetadata) with EF configs and an additive migration.
ReleaseDto.ReleaseType is now nullable, nulled for non-Cut at the converter.
Existing releases default to Cut via column default; no data migration.

DeepDrftModels/DTOs/MixMetadataDto.cs

@@ -0,0 +1,10 @@
+namespace DeepDrftModels.DTOs;
+
+// Mirror of MixMetadata (Phase 9). No `required` members — BlazorBlocks's Manager<> generic
+// constraint requires `new()`, which does not compose with required members. TrackConverter assigns
+// every field on the round-trip, so an empty default is never observable.
+public class MixMetadataDto
+{
+    public long ReleaseId { get; set; }
+    public string WaveformEntryKey { get; set; } = string.Empty;
+}

DeepDrftModels/DTOs/ReleaseDto.cs

@@ -14,7 +14,16 @@ public class ReleaseDto : BaseModel
     public string? Genre { get; set; }
     public DateOnly? ReleaseDate { get; set; }
     public string? ImagePath { get; set; }
-    public ReleaseType ReleaseType { get; set; } = ReleaseType.Single;
+    public ReleaseMedium Medium { get; set; } = ReleaseMedium.Cut;
+
+    // Nullable: meaningful only for Cut releases. TrackConverter nulls it for Session/Mix at the
+    // mapping point. One producer enforces the rule; no consumer depends on a non-null value.
+    public ReleaseType? ReleaseType { get; set; }
+
+    // Medium-specific satellites. Populated only for the matching medium; null otherwise.
+    public SessionMetadataDto? SessionMetadata { get; set; }
+    public MixMetadataDto? MixMetadata { get; set; }
+
     public long? CreatedByUserId { get; set; }
 
     // Read-model field: count of non-deleted tracks in this release. Not on ReleaseEntity — the

DeepDrftModels/DTOs/SessionMetadataDto.cs

@@ -0,0 +1,10 @@
+namespace DeepDrftModels.DTOs;
+
+// Mirror of SessionMetadata (Phase 9). No `required` members — BlazorBlocks's Manager<> generic
+// constraint requires `new()`, which does not compose with required members. TrackConverter assigns
+// every field on the round-trip, so an empty default is never observable.
+public class SessionMetadataDto
+{
+    public long ReleaseId { get; set; }
+    public string HeroImageEntryKey { get; set; } = string.Empty;
+}

DeepDrftModels/Entities/MixMetadata.cs

@@ -0,0 +1,17 @@
+using Models.Entities;
+
+namespace DeepDrftModels.Entities;
+
+// 1:1 satellite for Mix-medium releases (Phase 9). One row per Mix ReleaseEntity, keyed by a unique
+// ReleaseId FK (the 1:1 enforcement lives in MixMetadataConfiguration). Carries the entry key for
+// the preprocessed high-resolution waveform datum.
+//
+// Inherits Id, CreatedAt, UpdatedAt, IsDeleted from BaseEntity (Cerebellum.BlazorBlocks.Models).
+// BaseEntity ships the audit columns but does not declare IEntity itself, so subclasses declare it
+// explicitly to satisfy the generic constraints on Repository<>/Manager<>/etc.
+public class MixMetadata : BaseEntity, IEntity
+{
+    public long ReleaseId { get; set; }
+    public ReleaseEntity Release { get; set; } = null!;
+    public required string WaveformEntryKey { get; set; }
+}

DeepDrftModels/Entities/ReleaseEntity.cs

@@ -18,6 +18,13 @@ public class ReleaseEntity : BaseEntity, IEntity
     public DateOnly? ReleaseDate { get; set; }
     public string? ImagePath { get; set; }
     public ReleaseType ReleaseType { get; set; } = ReleaseType.Single;
+    public ReleaseMedium Medium { get; set; } = ReleaseMedium.Cut;
     public long? CreatedByUserId { get; set; }
     public ICollection<TrackEntity> Tracks { get; set; } = new List<TrackEntity>();
+
+    // 1:1 satellites selected by Medium. Null unless this release is the matching medium —
+    // Session releases carry SessionMetadata, Mix releases carry MixMetadata, Cut releases carry
+    // neither (ReleaseType on this table is their discriminator data).
+    public SessionMetadata? SessionMetadata { get; set; }
+    public MixMetadata? MixMetadata { get; set; }
 }

DeepDrftModels/Entities/SessionMetadata.cs

@@ -0,0 +1,17 @@
+using Models.Entities;
+
+namespace DeepDrftModels.Entities;
+
+// 1:1 satellite for Session-medium releases (Phase 9). One row per Session ReleaseEntity, keyed by
+// a unique ReleaseId FK (the 1:1 enforcement lives in SessionMetadataConfiguration). Carries the
+// hero-image entry key into the Image vault.
+//
+// Inherits Id, CreatedAt, UpdatedAt, IsDeleted from BaseEntity (Cerebellum.BlazorBlocks.Models).
+// BaseEntity ships the audit columns but does not declare IEntity itself, so subclasses declare it
+// explicitly to satisfy the generic constraints on Repository<>/Manager<>/etc.
+public class SessionMetadata : BaseEntity, IEntity
+{
+    public long ReleaseId { get; set; }
+    public ReleaseEntity Release { get; set; } = null!;
+    public required string HeroImageEntryKey { get; set; }
+}

DeepDrftModels/Enums/ReleaseMedium.cs

@@ -0,0 +1,16 @@
+namespace DeepDrftModels.Enums;
+
+/// <summary>
+/// The medium of a release — the Phase 9 discriminator that selects which metadata shape applies.
+/// </summary>
+public enum ReleaseMedium
+{
+    /// <summary>Studio recording. Uses <see cref="ReleaseType"/> (Single/EP/Album). The default.</summary>
+    Cut,
+
+    /// <summary>Single live track plus a hero image. Detail in <c>SessionMetadata</c>.</summary>
+    Session,
+
+    /// <summary>Single long track plus a preprocessed high-resolution waveform datum. Detail in <c>MixMetadata</c>.</summary>
+    Mix
+}