feat(progression): json stores on a real filesystem (slice 8)

new progression.adapters project, no engine reference. Stores take a
directory path; Godot resolves user:// with GlobalizePath and passes it
in, which is what makes them testable at all - originally I'd written
this slice off as untestable.

version lives in a file envelope, not the snapshot, so the domain only
knows the current shape. A newer-build save reports Corrupt with a
reason instead of masquerading as "no save" and getting overwritten.

atomic write via temp + rename. One file per aggregate: saving a run
leaves the profile file byte-identical, asserted.

guard rail fixed - it was matching prose in doc comments, now anchored
to using-directives plus a project.assets.json check. 63 tests.

progression.adapters/Mr.BrickAdventures.Progression.Adapters.csproj

@@ -0,0 +1,21 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <ItemGroup>
+    <ProjectReference Include="..\progression\Mr.BrickAdventures.Progression.csproj" />
+  </ItemGroup>
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <RootNamespace>Mr.BrickAdventures.Progression.Adapters</RootNamespace>
+
+    <!-- Required on assemblies referenced by a Godot project. -->
+    <EnableDynamicLoading>true</EnableDynamicLoading>
+  </PropertyGroup>
+
+  <!-- Deliberately no engine reference. These adapters take a plain directory path; Godot resolves
+       user:// to an absolute path and passes it in, which is what keeps them testable. -->
+
+
+</Project>