Give plugins access to device-wide config, and a global scroll frame rate

The sports scoreboards read `getattr(self, 'global_config', {})` to find a
shared scroll frame rate, but nothing ever set that attribute: the loader
constructs plugins with only plugin_id/config/display_manager/cache_manager/
plugin_manager (plugin_loader.py:671), `global_config` appears nowhere in
src/, no plugin manager assigns it, and BasePlugin has no __getattr__ to
synthesize it. The lookup always returned {}, so the ten scroll_display.py
copies that thread target_fps through to ScrollHelper could never fire on any
core. There was also no global target_fps to find -- the only one in the
template is display.vegas_scroll.target_fps, which is Vegas-scoped.

Adds the missing half:

- `BasePlugin.global_config` resolves the full config via
  plugin_manager.config_manager, then cache_manager.config_manager, then {}.
  Same order the sports timezone helpers already use. Exceptions are swallowed
  to debug so an unreadable config can never stop a plugin loading, and a
  non-dict result is rejected rather than handed to callers that will .get()
  it and feed the result to numeric code.
- A top-level `target_fps` (default 100), exposed on the General tab and
  validated 30-200 on save to match ScrollHelper.set_target_fps -- which
  clamps silently, so a rejected save reports a value that would otherwise
  appear to save and then behave differently.

The property has a setter deliberately. news, stock-news, ledmatrix-stocks,
ledmatrix-elections, ledmatrix-leaderboard and nfl-draft all assign
`self.global_config = config.get('global', {})`; without a setter that raises
"property has no setter" and those six plugins stop loading. Reproduced, then
pinned with a test.

target_fps is also kept out of the `is_general_update` key list: that branch
treats a missing web_display_autostart as an unchecked box, so counting a
target_fps-only POST as a General save would silently switch autostart off.

Verified end to end: config.json -> BasePlugin.global_config ->
scroll_display's existing block -> ScrollHelper.target_fps 120 -> 100, with no
plugin-side change needed. Suite 1441 passed; the 4 failures
(test_display_dirty_tracking, test_web_api::test_get_system_status, two in
test_state_reconciliation) are pre-existing and reproduce identically on a
clean tree.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KEZK1P1Q1fu5pcuVrkrCFZ

test/test_web_api.py

@@ -167,6 +167,63 @@ class TestConfigAPI:
             'enabled': True, 'copies': 2, 'axis': 'vertical',
         }
 
+    def test_save_target_fps(self, client, mock_config_manager):
+        """The device-wide scroll frame rate persists as a top-level int."""
+        response = client.post(
+            '/api/v3/config/main',
+            data={'target_fps': '90'},
+            content_type='application/x-www-form-urlencoded',
+        )
+
+        assert response.status_code == 200
+        saved = mock_config_manager.save_config_atomic.call_args[0][0]
+        # Must be the coerced int, not the raw form string -- the generic
+        # remaining-keys loop would otherwise write '90' back over it.
+        assert saved['target_fps'] == 90
+
+    def test_save_target_fps_alone_does_not_reset_other_general_settings(
+            self, client, mock_config_manager):
+        """A target_fps-only POST must not be treated as a full General-tab save.
+
+        The general branch reads web_display_autostart as an unchecked-checkbox
+        (absent means False), so counting target_fps as a general update would
+        silently switch autostart off for anyone setting only the frame rate.
+        """
+        mock_config_manager.load_config.return_value['web_display_autostart'] = True
+
+        response = client.post(
+            '/api/v3/config/main',
+            data={'target_fps': '90'},
+            content_type='application/x-www-form-urlencoded',
+        )
+
+        assert response.status_code == 200
+        saved = mock_config_manager.save_config_atomic.call_args[0][0]
+        assert saved['web_display_autostart'] is True
+
+    @pytest.mark.parametrize('value', ['20', '250', 'fast'])
+    def test_save_target_fps_rejects_out_of_range(self, client, mock_config_manager, value):
+        """Values ScrollHelper would silently clamp are reported instead."""
+        response = client.post(
+            '/api/v3/config/main',
+            data={'target_fps': value},
+            content_type='application/x-www-form-urlencoded',
+        )
+
+        assert response.status_code == 400
+
+    def test_save_target_fps_accepts_bounds(self, client, mock_config_manager):
+        """Both endpoints of the documented range are valid."""
+        for value in ('30', '200'):
+            response = client.post(
+                '/api/v3/config/main',
+                data={'target_fps': value},
+                content_type='application/x-www-form-urlencoded',
+            )
+            assert response.status_code == 200, f"{value} should be accepted"
+            saved = mock_config_manager.save_config_atomic.call_args[0][0]
+            assert saved['target_fps'] == int(value)
+
     def test_save_double_sided_unchecked_disables(self, client, mock_config_manager):
         """An omitted 'enabled' checkbox is saved as disabled, not left stale."""
         response = client.post(