fix(vector): guard unbound doc_task + address review nits (#891)

Round-1 review on PR #891:
- Guard processor_task's broad except handler against an unbound doc_task
  (mirrors multi_user_processor_task): initialise doc_task=None before the loop
  and branch the error log. Fixes a latent NameError if receive() raises a
  non-TimeoutError/EndOfStream before the first document binds. Regression test
  added.
- Drop the unnecessary `from __future__ import annotations` in vector/_errors.py
  and express format_exception_group's non-group fast path as an explicit
  isinstance check.
- Add a copy_resource Destination-header encoding test (analogue to MOVE);
  strengthen the ExceptionGroup test to assert the full leaf repr survives.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

nextcloud_mcp_server/vector/_errors.py

@@ -9,8 +9,6 @@ exceptions so log lines name the actual cause; pair it with ``exc_info=True`` to
 keep the full traceback.
 """
 
-from __future__ import annotations
-
 
 def format_exception_group(exc: BaseException) -> str:
     """Return a concise, leaf-naming string for ``exc``.
@@ -20,9 +18,9 @@ def format_exception_group(exc: BaseException) -> str:
     result is meant for the human-readable portion of a log message, not for
     parsing.
     """
-    leaves = _flatten(exc)
-    if len(leaves) == 1 and leaves[0] is exc:
+    if not isinstance(exc, BaseExceptionGroup):
         return repr(exc)
+    leaves = _flatten(exc)
     return f"{len(leaves)} sub-exception(s): " + "; ".join(repr(e) for e in leaves)
 
 

nextcloud_mcp_server/vector/processor.py

@@ -236,6 +236,11 @@ async def processor_task(
     # Signal that the task has started and is ready
     task_status.started()
 
+    # Initialised before the loop so the broad except handler below can't hit an
+    # unbound name if receive() itself raises a non-TimeoutError/EndOfStream
+    # exception on the very first iteration (mirrors multi_user_processor_task).
+    doc_task: DocumentTask | None = None
+
     while not shutdown_event.is_set():
         try:
             # Get document with timeout (allows checking shutdown)
@@ -265,14 +270,22 @@ async def processor_task(
             break
 
         except Exception as e:
-            logger.error(
-                "Processor %s error processing %s_%s: %s",
-                worker_id,
-                doc_task.doc_type,
-                doc_task.doc_id,
-                format_exception_group(e),
-                exc_info=True,
-            )
+            if doc_task is not None:
+                logger.error(
+                    "Processor %s error processing %s_%s: %s",
+                    worker_id,
+                    doc_task.doc_type,
+                    doc_task.doc_id,
+                    format_exception_group(e),
+                    exc_info=True,
+                )
+            else:
+                logger.error(
+                    "Processor %s error: %s",
+                    worker_id,
+                    format_exception_group(e),
+                    exc_info=True,
+                )
             # Continue to next document (no task_done() needed with streams)
 
     logger.info("Processor %s stopped", worker_id)