test: address review feedback — fixture lifecycle, test names, ClassVar

- ci-fixture-plugin: call display_manager.clear() before rendering (per
  plugin guidelines — the fixture should model a well-behaved plugin),
  add a class docstring, and document why Pillow is deliberately not
  pinned in its requirements.txt (core dependency; harness installs
  nothing).
- Rename two tests whose names contradicted their assertions:
  test_unparseable_core_version_is_compatible ->
  test_unparseable_core_with_high_floor_is_blocked, and
  test_unreadable_secrets_file... -> test_corrupt_secrets_file...
- Annotate TestGetSchemaProperty.SCHEMA as ClassVar (RUF012).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NohXi78cwsAKtN1sCfxjUh

test/fixtures/plugins/ci-fixture-plugin/manager.py

@@ -16,10 +16,16 @@ from src.plugin_system.base_plugin import BasePlugin
 
 
 class CIFixturePlugin(BasePlugin):
+    """Deterministic CI-only fixture plugin: renders a border + diagonals
+    pattern sized from the display's declared dimensions. Never shipped to
+    devices; exists solely so the plugin safety harness has a real plugin
+    to exercise in CI."""
+
     def update(self) -> None:
         """Nothing to fetch — the render is self-contained."""
 
     def display(self, force_clear: bool = False) -> None:
+        self.display_manager.clear()
         width = self.display_manager.matrix.width
         height = self.display_manager.matrix.height
         border = tuple(self.config.get("border_color", [0, 255, 0]))

test/fixtures/plugins/ci-fixture-plugin/requirements.txt

@@ -1 +1,7 @@
 # No dependencies — the fixture must load in any environment.
+#
+# Pillow is deliberately NOT pinned here even though manager.py imports
+# PIL: it is a core LEDMatrix dependency (see the repo-root
+# requirements.txt), so it is always present wherever the harness runs,
+# and the harness loads plugins with install_deps=False anyway. Pinning
+# it here would only invite a needless pip install during test runs.

test/test_compatibility.py

@@ -216,7 +216,7 @@ class TestCheck:
         assert ok is False
         assert "2.0.0 - 2.9.9" in reason
 
-    def test_unparseable_core_version_is_compatible(self):
+    def test_unparseable_core_with_high_floor_is_blocked(self):
         manifest = {"min_ledmatrix_version": "3.2.0",
                     "compatible_versions": [">=3.2.0"]}
         # An unparseable core version is "unknown", not "old"... but note

test/test_config_manager_secrets.py

@@ -99,9 +99,9 @@ class TestSaveStripsSecrets:
         on_disk = json.loads((tmp_path / "config.json").read_text())
         assert on_disk == {"timezone": "UTC"}
 
-    def test_unreadable_secrets_file_writes_secrets_to_config_json(self, tmp_path):
+    def test_corrupt_secrets_file_writes_secrets_to_config_json(self, tmp_path):
         # SUSPECTED BUG (characterized, not fixed): when the secrets file is
-        # unreadable/corrupt at save time, save_config proceeds without
+        # corrupt (or otherwise unloadable) at save time, save_config proceeds without
         # stripping — writing the merged secrets into config.json in
         # plaintext. The code comments acknowledge the tradeoff (it prevents
         # data loss); this test pins the behavior so any future change to it

test/web_interface/test_api_v3_helpers.py

@@ -11,6 +11,7 @@ characterized quirks marked below.
 
 import sys
 from pathlib import Path
+from typing import Any, ClassVar, Dict
 
 import pytest
 
@@ -153,7 +154,7 @@ class TestParseFormValue:
 
 
 class TestGetSchemaProperty:
-    SCHEMA = {
+    SCHEMA: ClassVar[Dict[str, Any]] = {
         "properties": {
             "brightness": {"type": "integer"},
             "customization": {