refactor(plugins): the display publishes plugin runtime state; retire plugin_state.json (#690)

Stage 2 of the web plugin catalog, after #688.

- The display publishes a plugin runtime snapshot (plugin_runtime.py) to
  the shared cache: per plugin loaded, lifecycle state, a short redacted
  error summary, the version it loaded and when, plus published_at /
  stale_after / running. Written on change (throttled to 10 s; the
  RUNNING/ENABLED flip of an ordinary update is not a change) and once a
  minute otherwise; cleanup() publishes running: false.
- The web reads it back and restores loaded / state / error_info in
  /api/v3/plugins/installed (plus loaded_version, loaded_at and
  data.runtime). Only a live snapshot counts; stale, stopped or missing
  answers null and says which.
- data/plugin_state.json is retired: every reader and writer moved to
  config + disk (desired) or the snapshot (observed). Nothing in it was
  non-derivable, so nothing is migrated and an existing file is left
  unread. The web-side PluginStateManager (state_manager.py) is removed;
  the display's plugin_state.PluginStateManager is the only state machine.
- StateReconciliation compares config + disk with the snapshot, reporting
  enabled-but-not-loaded and older-version-loaded as no_action findings.
- Backups list installed manifests with enabled from config.json.

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

web_interface/app.py

@@ -39,7 +39,6 @@ from src.plugin_system.store_manager import PluginStoreManager
 from src.plugin_system.saved_repositories import SavedRepositoriesManager
 from src.plugin_system.schema_manager import SchemaManager
 from src.plugin_system.operation_queue import PluginOperationQueue
-from src.plugin_system.state_manager import PluginStateManager
 from src.plugin_system.operation_history import OperationHistory
 
 _JOURNALCTL = shutil.which('journalctl')
@@ -158,13 +157,10 @@ plugin_catalog = PluginCatalog(
 # Initialize operation queue for plugin operations
 operation_queue = PluginOperationQueue(max_history=500)
 
-# Initialize plugin state manager
-# Use lazy_load=True to defer file loading until first use (improves startup time)
-plugin_state_manager = PluginStateManager(
-    state_file=str(project_root / "data" / "plugin_state.json"),
-    auto_save=True,
-    lazy_load=True
-)
+# No plugin state file: data/plugin_state.json is retired. Desired state is
+# config.json plus the plugins on disk, observed state is the runtime
+# snapshot the display publishes (src/plugin_system/plugin_runtime.py). An
+# existing file is left where it is, unread; see docs/ARCHITECTURE.md.
 
 # Initialize operation history
 # Use lazy_load=True to defer file loading until first use (improves startup time)
@@ -194,7 +190,6 @@ api_v3.plugin_store_manager = plugin_store_manager
 api_v3.saved_repositories_manager = saved_repositories_manager
 api_v3.schema_manager = schema_manager
 api_v3.operation_queue = operation_queue
-api_v3.plugin_state_manager = plugin_state_manager
 api_v3.operation_history = operation_history
 # Initialize cache manager for API endpoints
 from src.cache_manager import CacheManager
@@ -965,12 +960,12 @@ def _run_startup_reconciliation() -> None:
 
     try:
         from src.plugin_system.state_reconciliation import StateReconciliation
+        from src.plugin_system.plugin_runtime import read_plugin_runtime
         reconciler = StateReconciliation(
-            state_manager=plugin_state_manager,
             config_manager=config_manager,
-            plugin_manager=plugin_catalog,
             plugins_dir=plugins_dir,
-            store_manager=plugin_store_manager
+            store_manager=plugin_store_manager,
+            runtime_source=lambda: read_plugin_runtime(api_v3.cache_manager),
         )
         result = reconciler.reconcile_state()
         if result.inconsistencies_found: