refactor: move validation tests into dandi/validate/tests/

- test_validate.py → dandi/validate/tests/test_core.py
- test_validate_types.py → dandi/validate/tests/test_types.py
- Update relative imports in moved test files
- Fix circular import: don't eagerly import core in __init__.py

Co-Authored-By: Claude Code 2.1.63 / Claude Opus 4.6 <noreply@anthropic.com>

Author: yarikoptic

dandi/validate/__init__.py

@@ -10,9 +10,12 @@
 - core: Main validation functions (validate, validate_bids)
 - types: Data types and models (ValidationResult, Origin, Severity, etc.)
 - io: JSONL read/write utilities for validation results
+
+Note: core is NOT eagerly imported here to avoid circular imports
+(core → dandi.files → dandi.validate.types → dandi.validate.__init__).
+Import from dandi.validate.core directly for validate/validate_bids.
 """
 
-from .core import validate, validate_bids
 from .types import (
     ORIGIN_INTERNAL_DANDI,
     ORIGIN_VALIDATION_DANDI,
@@ -41,6 +44,4 @@
     "Standard",
     "ValidationResult",
     "Validator",
-    "validate",
-    "validate_bids",
 ]

dandi/validate/tests/__init__.py

@@ -4,11 +4,8 @@
 
 import pytest
 
-from .fixtures import BIDS_TESTDATA_SELECTION
-from .. import __version__
-from ..consts import dandiset_metadata_file
-from ..validate.core import validate
-from ..validate.types import (
+from ..core import validate
+from ..types import (
     Origin,
     OriginType,
     Scope,
@@ -17,6 +14,9 @@
     ValidationResult,
     Validator,
 )
+from ... import __version__
+from ...consts import dandiset_metadata_file
+from ...tests.fixtures import BIDS_TESTDATA_SELECTION
 
 
 def test_validate_nwb_error(simple3_nwb: Path) -> None: