refactor(workflow-file): phase1 migrate workflow file deps with compatibility bridge

Implement phase 1 of the file module migration by moving workflow-facing file primitives to core.workflow.file while keeping core.file as a temporary compatibility layer.

What this commit changes
- Add core.workflow.file package (constants/enums/models/helpers/file_manager/tool_file_parser).
- Add protocol-based runtime binding in core.workflow.file.runtime and core.workflow.file.protocols.
- Add application adapter core.app.workflow.file_runtime and bind runtime in extensions.ext_storage.init_app.
- Bind runtime in tests via tests/conftest.py.
- Migrate workflow-only imports from core.file.* to core.workflow.file.* across workflow runtime/nodes/entry/encoder and workflow node factory.
- Update workflow unit tests to patch/import the new workflow file namespace.
- Remove workflow-external-imports ignore_imports entries related to core.file from .importlinter.

Compatibility guarantee for phase split
- Keep core.file import path available in this phase by replacing core/file/*.py with forwarding bridge modules that re-export core.workflow.file symbols.
- Preserve runtime behavior and isinstance(File) identity consistency while non-workflow modules are still on legacy import paths.

Notes
- This commit intentionally does not remove core.file. Full repository replacement and bridge removal are handled in phase 2.

api/core/workflow/nodes/llm/file_saver.py

@@ -4,10 +4,10 @@ import typing as tp
 from sqlalchemy import Engine
 
 from constants.mimetypes import DEFAULT_EXTENSION, DEFAULT_MIME_TYPE
-from core.file import File, FileTransferMethod, FileType
 from core.helper import ssrf_proxy
 from core.tools.signature import sign_tool_file
 from core.tools.tool_file_manager import ToolFileManager
+from core.workflow.file import File, FileTransferMethod, FileType
 from extensions.ext_database import db as global_db
 
 

api/core/workflow/nodes/llm/llm_utils.py

@@ -7,7 +7,6 @@ from sqlalchemy.orm import Session
 from configs import dify_config
 from core.app.entities.app_invoke_entities import ModelConfigWithCredentialsEntity
 from core.entities.provider_entities import ProviderQuotaType, QuotaUnit
-from core.file.models import File
 from core.memory.token_buffer_memory import TokenBufferMemory
 from core.model_manager import ModelInstance, ModelManager
 from core.model_runtime.entities.llm_entities import LLMUsage
@@ -16,6 +15,7 @@ from core.model_runtime.model_providers.__base.large_language_model import Large
 from core.prompt.entities.advanced_prompt_entities import MemoryConfig
 from core.variables.segments import ArrayAnySegment, ArrayFileSegment, FileSegment, NoneSegment, StringSegment
 from core.workflow.enums import SystemVariableKey
+from core.workflow.file.models import File
 from core.workflow.nodes.llm.entities import ModelConfig
 from core.workflow.runtime import VariablePool
 from extensions.ext_database import db

api/core/workflow/nodes/llm/node.py

@@ -12,7 +12,6 @@ from typing import TYPE_CHECKING, Any, Literal
 from sqlalchemy import select
 
 from core.app.entities.app_invoke_entities import ModelConfigWithCredentialsEntity
-from core.file import File, FileTransferMethod, FileType, file_manager
 from core.helper.code_executor import CodeExecutor, CodeLanguage
 from core.llm_generator.output_parser.errors import OutputParserError
 from core.llm_generator.output_parser.structured_output import invoke_llm_with_structured_output
@@ -65,6 +64,7 @@ from core.workflow.enums import (
     WorkflowNodeExecutionMetadataKey,
     WorkflowNodeExecutionStatus,
 )
+from core.workflow.file import File, FileTransferMethod, FileType, file_manager
 from core.workflow.node_events import (
     ModelInvokeCompletedEvent,
     NodeEventBase,
@@ -101,7 +101,7 @@ from .exc import (
 from .file_saver import FileSaverImpl, LLMFileSaver
 
 if TYPE_CHECKING:
-    from core.file.models import File
+    from core.workflow.file.models import File
     from core.workflow.runtime import GraphRuntimeState
 
 logger = logging.getLogger(__name__)