Fix remaining pre-existing ty diagnostics in test files

Completes the isinstance/cast narrowing + Optional-field assert pattern
across the last batch of test files. custom_components and tests are
now both fully clean under ruff check, ruff format --check, and ty check.

tests/test_capability.py

@@ -13,8 +13,14 @@ def test_capability_defaults():
 
 def test_capability_is_frozen():
     c = Capability(href="/kidslock/vs/0", entities=())
+    # setattr(), not `c.href = ...` -- `href` is a read-only property to the
+    # type checker (frozen dataclass field), so a literal attribute
+    # assignment doesn't type-check; setattr's signature is untyped enough
+    # to accept it, and it still goes through the same frozen __setattr__
+    # at runtime, so this is still a faithful test of the frozen guarantee.
+    attr_name = "href"
     try:
-        setattr(c, "href", "/other/vs/0")
+        setattr(c, attr_name, "/other/vs/0")
     except Exception:
         return
     raise AssertionError("expected frozen dataclass")