Initial commit: Theriapolis baseline at port/godot branch point

Captures the pre-Godot-port state of the codebase. This is the rollback
anchor for the Godot port (M0 of theriapolis-rpg-implementation-plan-godot-port.md).
All Phase 0 through Phase 6.5 work is included; Phase 7 is in flight.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Theriapolis.Tests/Persistence/V5ToV6MigrationTests.cs

@@ -0,0 +1,74 @@
+using Theriapolis.Core;
+using Theriapolis.Core.Persistence;
+using Theriapolis.Core.Persistence.SaveMigrations;
+using Xunit;
+
+namespace Theriapolis.Tests.Persistence;
+
+/// <summary>
+/// Phase 6 M2 — additive V5→V6 migration. Unlike V4→V5 (rejection), v5
+/// saves are accepted and migrated up by zero-filling the new typed
+/// reputation containers.
+/// </summary>
+public sealed class V5ToV6MigrationTests
+{
+    [Fact]
+    public void V5Header_IsAcceptedByMigration()
+    {
+        var header = new SaveHeader { Version = 5 };
+        Assert.True(SaveCodec.IsCompatible(header),
+            "v5 must remain readable post-Phase-6 (MIN_VERSION = 5).");
+
+        var body = new SaveBody();
+        bool ok = Migrations.MigrateUp(header, body);
+        Assert.True(ok);
+        Assert.Equal(C.SAVE_SCHEMA_VERSION, header.Version);
+    }
+
+    [Fact]
+    public void V6_NewBody_HasEmptyReputationState()
+    {
+        var body = new SaveBody();
+        Assert.NotNull(body.ReputationState);
+        Assert.Empty(body.ReputationState.FactionStandings);
+        Assert.Empty(body.ReputationState.Personal);
+        Assert.Empty(body.ReputationState.Ledger);
+    }
+
+    [Fact]
+    public void V5SaveBody_AfterMigration_HasEmptyReputation()
+    {
+        // Construct what a Phase-5-saved body might look like — v5 fields
+        // (Player, Clock, ModifiedChunks, ModifiedWorldTiles, Flags,
+        // PlayerCharacter, NpcRoster, ActiveEncounter), no v6 fields.
+        var header = new SaveHeader { Version = 5 };
+        var body = new SaveBody
+        {
+            Player = new() { Name = "Old Hand", PositionX = 50, PositionY = 50 },
+        };
+        body.Flags["debug-flag"] = 1;
+
+        bool ok = Migrations.MigrateUp(header, body);
+        Assert.True(ok);
+        // Migration chains all the way up to the current schema version.
+        Assert.Equal(C.SAVE_SCHEMA_VERSION, header.Version);
+
+        // V5 fields must survive untouched.
+        Assert.Equal("Old Hand", body.Player.Name);
+        Assert.Equal(1, body.Flags["debug-flag"]);
+
+        // V6 fields must be empty (the migration does not synthesise data).
+        Assert.NotNull(body.ReputationState);
+        Assert.Empty(body.ReputationState.FactionStandings);
+        Assert.Empty(body.ReputationState.Personal);
+    }
+
+    [Fact]
+    public void NewSaveHeader_DefaultsToCurrentSchemaVersion()
+    {
+        // Schema version increments per phase (Phase 6 = v6, Phase 6.5 = v7);
+        // SaveHeader picks up the constant.
+        var header = new SaveHeader();
+        Assert.Equal(C.SAVE_SCHEMA_VERSION, header.Version);
+    }
+}