doc: README and CLAUDE.md for the uv workflow; fix debug env var and platform claims

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

tests/README.md

@@ -4,14 +4,14 @@ Contained is the early stages of unit testing for app_skellington framework.
 
 Usage
 -----
-Run all tests (cwd is testing directory):
+Run all tests (from the repo root):
 
-    pytest .
+    uv run pytest
 
 Run test by keyword:
 
-    pytest -k "<test keyword>" .
+    uv run pytest -k "<test keyword>"
 
 Run test by directory:
 
-    pytest <dirname>
+    uv run pytest tests/<dirname>