fix(display): a raising display() counts as a circuit-breaker failure (#707)

The first-frame dispatch (_dispatch_first_frame) now asks PluginExecutor.execute_display() to re-raise (raise_errors=True) and records a raise inside the executor as a breaker failure, with the original exception as last_error, instead of a success. The screen is still an empty pass and rotation is unchanged; a hung display() is still recorded once, as a hang. The run-loop golden trace plugin_error.json is regenerated (crashy now records health failures and is skipped by the breaker), and behaviour 7 is dropped from docs/RUN_LOOP_REDESIGN.md.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/display_controller.py

@@ -41,6 +41,7 @@ from src.config_service import ConfigService
 from src.cache_manager import CacheManager
 from src.font_manager import FontManager
 from src.logging_config import get_logger
+from src.exceptions import PluginError
 from src.common.sync_manager import DisplaySyncManager, SyncRole
 from src.ipc.server import ControlServer, start_control_server
 from src.vegas_mode.render_pipeline import SYNC_SEND_INTERVAL
@@ -2499,6 +2500,8 @@ class DisplayController:
             display_lock = pm.get_plugin_lock(plugin_id) if pm else None
             can_display = display_lock is None or display_lock.acquire(blocking=False)
             display_hung = False
+            # Set when display() raised inside the executor.
+            display_error: Optional[Exception] = None
 
             if display_lock is None:
                 # Only when plugin loading failed part-way.
@@ -2556,8 +2559,23 @@ class DisplayController:
                         # the SimpleNamespace built above -- a
                         # fresh callable every call, so nothing
                         # there can ever cache.
-                        accepts_display_mode=_accepts_display_mode
+                        accepts_display_mode=_accepts_display_mode,
+                        # A raise must reach the breaker as a
+                        # failure. As a bare False it read as
+                        # "no content" and was recorded as a
+                        # success, so the breaker never tripped
+                        # on a plugin that raises every time.
+                        raise_errors=True
                     )
+                except PluginError as exc:
+                    # display() raised. The executor has logged
+                    # and recorded it, and _display_target's
+                    # finally released the lock. The screen is
+                    # an empty pass, as before; only the health
+                    # record changes. Keep what display() raised
+                    # as last_error, not the executor's wrapper.
+                    display_error = exc.__cause__ or exc
+                    result = False
                 except Exception:  # pragma: no cover - defensive;
                     # execute_display catches everything
                     # internally, but guarantee the lock is
@@ -2589,10 +2607,15 @@ class DisplayController:
             # frame, not a real success, and must not clear
             # force_change or the pending mode-switch clear will
             # be lost when display() finally does run.
+            # A hang was already recorded as a failure by
+            # record_display_hang, so it records nothing here.
             if can_display:
                 health_tracker = self._health_tracker()
                 if health_tracker is not None and not display_hung:
-                    health_tracker.record_success(plugin_id)
+                    if display_error is not None:
+                        health_tracker.record_failure(plugin_id, display_error)
+                    else:
+                        health_tracker.record_success(plugin_id)
                 self.force_change = False
         except Exception as exc:  # pylint: disable=broad-except
             logger.exception("Error displaying %s", self.current_display_mode)