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/Dungeons/Phase7ConstantsTests.cs

@@ -0,0 +1,75 @@
+using Theriapolis.Core;
+using Xunit;
+
+namespace Theriapolis.Tests.Dungeons;
+
+/// <summary>
+/// Phase 7 M0 — schema integrity tests for the Phase 7 constants. These
+/// guard against silent regressions in:
+///   - <see cref="C.SAVE_SCHEMA_VERSION"/> (must == 8 at Phase 7 ship)
+///   - The 4 new RNG sub-streams (must be unique vs every existing stream)
+///   - Dungeon size bands (must be a coherent ladder)
+///   - Movement-cost multipliers (must be ≥ 1.0; squeezing must dominate)
+/// </summary>
+public sealed class Phase7ConstantsTests
+{
+    [Fact]
+    public void SaveSchemaVersion_IsEight()
+    {
+        Assert.Equal(8, C.SAVE_SCHEMA_VERSION);
+    }
+
+    [Fact]
+    public void DungeonRngSubStreams_AreDistinctFromAllExistingStreams()
+    {
+        // Collect every named ulong RNG sub-stream by reflection. Each
+        // must be unique — a collision means two independent streams share
+        // a seed, breaking the dice contract.
+        var fields = typeof(C).GetFields(System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Static)
+            .Where(f => f.IsLiteral && f.FieldType == typeof(ulong))
+            .ToArray();
+        var seen = new Dictionary<ulong, string>();
+        foreach (var f in fields)
+        {
+            ulong value = (ulong)f.GetRawConstantValue()!;
+            if (seen.TryGetValue(value, out var prior))
+                Assert.Fail($"RNG sub-stream collision: {f.Name} == {prior} ({value:X})");
+            seen[value] = f.Name;
+        }
+        // Belt-and-braces: assert the four Phase 7 streams exist.
+        Assert.Contains(C.RNG_DUNGEON_LAYOUT,   seen.Keys);
+        Assert.Contains(C.RNG_ROOM_PICK,        seen.Keys);
+        Assert.Contains(C.RNG_DUNGEON_POPULATE, seen.Keys);
+        Assert.Contains(C.RNG_DUNGEON_LOOT,     seen.Keys);
+    }
+
+    [Fact]
+    public void DungeonSizeBands_FormCoherentLadder()
+    {
+        Assert.True(C.DUNGEON_SMALL_ROOMS_MIN <= C.DUNGEON_SMALL_ROOMS_MAX);
+        Assert.True(C.DUNGEON_MED_ROOMS_MIN   <= C.DUNGEON_MED_ROOMS_MAX);
+        Assert.True(C.DUNGEON_LARGE_ROOMS_MIN <= C.DUNGEON_LARGE_ROOMS_MAX);
+        // Ladders don't overlap — a small dungeon's max < medium's min.
+        Assert.True(C.DUNGEON_SMALL_ROOMS_MAX < C.DUNGEON_MED_ROOMS_MIN);
+        Assert.True(C.DUNGEON_MED_ROOMS_MAX   < C.DUNGEON_LARGE_ROOMS_MIN);
+    }
+
+    [Fact]
+    public void MovementCostMultipliers_AreOrdered()
+    {
+        Assert.True(C.MOVE_COST_MISMATCH_LIGHT >= 1.0f,
+            "Mismatch must never give a speed bonus.");
+        Assert.True(C.MOVE_COST_MISMATCH_LIGHT < C.MOVE_COST_MISMATCH_MED);
+        Assert.True(C.MOVE_COST_MISMATCH_MED   < C.MOVE_COST_MISMATCH_HEAVY);
+    }
+
+    [Fact]
+    public void LockAndTrapDcs_AreOrdered()
+    {
+        Assert.True(C.LOCK_DC_TRIVIAL < C.LOCK_DC_EASY);
+        Assert.True(C.LOCK_DC_EASY    < C.LOCK_DC_MEDIUM);
+        Assert.True(C.LOCK_DC_MEDIUM  < C.LOCK_DC_HARD);
+        Assert.True(C.TRAP_DC_TRIVIAL < C.TRAP_DC_EASY);
+        Assert.True(C.TRAP_DC_EASY    < C.TRAP_DC_MEDIUM);
+    }
+}