fix(lora): import the sidecars and local images LoraManager really uses (#355)

The import, the legacy scan, the trigger-word cache and the image server
now share LoraManager's layout: sidecars beside the models (alongside) or
under the sidecar root (centralized), kept only when their model exists
inside a LoRA root. Each LoRA links its LoraManager preview and example
images where they are; CivitAI downloads run only for a LoRA without any
local image. The review adds skipped, with_local_media and the layout, and
offers no token when LoraManager's settings cannot be used; the legacy scan
reports the same reason without replacing anything.

find_lora_directories becomes default_lora_roots (no scan of the
LoraManager install); the preview and example-folder helpers it replaced
are removed. The trigger cache never raises into a running node.

tests/test_node_execution_contract.py

@@ -315,6 +315,25 @@ class TestLoraTriggerWords(NodeTestCase):
             )
         cache.load.assert_called_once_with("/loras")
 
+    def test_a_failing_discovery_logs_and_the_node_still_runs(self):
+        # #355: the trigger cache reads LoraManager's folders while a node
+        # runs; a folder that cannot be listed must never stop the node.
+        from py import lora_utils
+
+        cache = lora_utils.get_trigger_cache()
+        cache.clear()
+        self.addCleanup(cache.clear)
+        with (
+            mock.patch.dict(sys.modules, {"py.config": fake_integration_config(True)}),
+            mock.patch.object(
+                lora_utils, "discover_sidecars", side_effect=OSError("share gone")
+            ),
+            self.assertLogs("prompt_manager.lora_utils", level="WARNING") as logs,
+        ):
+            text = self.node._inject_lora_trigger_words("a cat <lora:neon:1>")
+        self.assertEqual(text, "a cat <lora:neon:1>")
+        self.assertIn("share gone", "\n".join(logs.output))
+
 
 class TestPromptManagerEncoding(NodeTestCase):
     node_cls = PromptManager