MAINT-21: tests read and patch the Controller through tools/main_files.py

Prepares the split of app/main.py's Controller into files by job, with no app
change. tools/main_files.py gives a test the text and the AST of main.py plus
the files split from it, and `live`, which sets a global in every file whose
functions read it (and raises when none does). Tests that read main.py's
source, and tests and replay tools that patch a main global (datetime,
compute, resolve, _mono, WRITE_BUDGET_S, ...), go through it, so they pass on
this layout and on the split one. test_split_patches.py fails when a test or
tool patches an app.main attribute that main.py no longer reads, or that
another file also reads. tools/maint21_same_ast.py proves every function,
method and module-level assignment of main.py at the base is found unchanged
in its new file.

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

goodwe_controller/test_defaults_pin.py

@@ -149,9 +149,15 @@ print("2. the mirrors, DISCOVERED from the tree rather than listed here")
 # `app/` for module-level assignments whose name ends in OPTION_DEFAULTS and
 # grades whatever it finds, so the seventh is covered on the commit that
 # introduces it. That is the property the six hand-written pins cannot have.
-MODULES = sorted(p.name for p in APP.glob("*.py"))
+sys.path.insert(0, str(HERE / "tools"))
+import main_files  # noqa: E402
+
+# MAINT-21: app/main.py stands for itself and the files split from it.
+MODULES = sorted(p.name for p in APP.glob("*.py")
+                 if p.name == "main.py" or p.name not in main_files.files())
 TREES = {name: ast.parse(io.open(APP / name, encoding="utf-8").read(), name)
          for name in MODULES}
+TREES["main.py"] = main_files.tree()
 
 MIRROR = {}          # schema key -> (module, table name, value)
 TABLES = []