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.tests/Mr.BrickAdventures.Progression.Tests.csproj

@@ -12,6 +12,7 @@
 
   <ItemGroup>
     <ProjectReference Include="..\progression\Mr.BrickAdventures.Progression.csproj" />
+    <ProjectReference Include="..\progression.adapters\Mr.BrickAdventures.Progression.Adapters.csproj" />
   </ItemGroup>
 
   <ItemGroup>