test(robot): close the real cache connection before simulating corruption

The two corruption-recovery tests replaced the live connection with a fake
one but never closed the real one. On Windows the orphaned handle kept
cache.db open, so the rebuild could not delete the file and reopened the
stale data, failing the assertions (read returned an entry, clear_all
returned 1). POSIX hid this because deleting an open file is allowed.

Closing the real connection first mirrors what _rebuild does in production,
where self._conn is always the real connection it closes before purging.

Author: d-biehl

tests/robotcode/robot/diagnostics/test_data_cache.py

@@ -320,7 +320,10 @@ def execute(self, *args: object, **kwargs: object) -> object:
             def close(self) -> None:
                 pass
 
-        # Simulate the live connection turning corrupt mid-session.
+        # Simulate the live connection turning corrupt mid-session. Close the real one
+        # first: otherwise it keeps cache.db open and _rebuild's purge cannot delete the
+        # file on Windows (production always closes the real connection in _rebuild).
+        cache._conn.close()
         cache._conn = _BoomConnection()  # type: ignore[assignment]
 
         # The read must not raise: _run detects the error, rebuilds, and retries.
@@ -346,6 +349,8 @@ def execute(self, *args: object, **kwargs: object) -> object:
             def close(self) -> None:
                 pass
 
+        # Close the real connection first so the corrupt file is not held open on Windows.
+        cache._conn.close()
         cache._conn = _BoomConnection()  # type: ignore[assignment]
 
         # clear_all is the path the "Clear Cache" command hits; it must recover, not raise.