fix(security): send a generic LoRA scan error to the browser

An unexpected exception's text could reach the page in the LoRA scan's
error frame, including a path or a model name. Those failures now send a
fixed message and keep the detail in the server log. Expected refusals keep
their wording, and an OSError still shows its reason and the file's basename.

Refs #552

py/api/lora_integration.py

@@ -44,6 +44,7 @@ _FILES_CHANGED = (
     "The LoRA metadata files changed during the scan; the previous imports "
     "were kept. Run the scan again."
 )
+_LORA_SCAN_FAILED = "The LoRA import failed. Check the server log for details."
 _IMPORTS_CHANGED = (
     "The imported LoRA prompts changed during the scan; the previous imports "
     "were kept. Run the scan again."
@@ -407,10 +408,21 @@ class LoraIntegrationMixin:
             return
         if isinstance(error, PlanChanged):
             message = _IMPORTS_CHANGED
-        elif isinstance(error, (LoraFilesChanged, LoraSettingsUnusable)):
+        elif isinstance(
+            error,
+            (
+                LoraFilesChanged,
+                LoraSettingsUnusable,
+                EmptyReplacement,
+                PairDependencyError,
+            ),
+        ):
             message = str(error)
-        else:
+        elif isinstance(error, OSError):
+            # Reduced to its reason and the file's basename.
             message = self._public_error(error)
+        else:
+            message = _LORA_SCAN_FAILED
         if isinstance(
             error,
             (

tests/test_api_lora.py

@@ -840,6 +840,23 @@ class TestLoraScanRoute(LoraAPITestCase):
             ("error", error["message"], 0),
         )
 
+    async def test_unexpected_scan_error_is_generic_in_the_stream(self):
+        self._enable()
+        secret = str(self.tmp_root / "x.db")
+        err = RuntimeError(f"could not open {secret}")
+        with patch.object(self.api.db, "replace_category_prompts", side_effect=err):
+            with self.assertLogs("prompt_manager.api", level="ERROR") as logs:
+                resp = await self.client.request("POST", "/prompt_manager/lora/scan")
+                body = await resp.text()  # the stream ends inside the patch
+        self.assertNotIn("x.db", body)
+        error = self._sse_events(body)[-1]
+        self.assertEqual(
+            (error["type"], error["status"], error["progress"]),
+            ("error", error["message"], 0),
+        )
+        self.assertIn("server log", error["message"])
+        self.assertIn(secret, "\n".join(logs.output))
+
     @staticmethod
     def _sse_events(text):
         return [