feat(files-mcp): business wrappers and Pydantic request models

Adds files_mcp/tools/requests.py with 9 Pydantic body models (one per
tool, since fastapi-mcp passes args as JSON body) and
files_mcp/tools/files.py with 9 thin wrappers that call path_guard
then fs_ops and return model_dump() form. Adds tests/unit/test_files_tool.py
covering happy path, sandbox escape, and KeyError/FileExistsError
propagation for each wrapper.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

files_mcp/tools/requests.py

@@ -0,0 +1,58 @@
+# coding=utf-8
+"""
+@Time   :2026/6/30
+@Author :tao.chen
+
+Pydantic body models for the FastAPI route layer. fastapi-mcp passes
+tool args as a JSON body, so every tool needs a model (even single-arg
+ones) — dict-typed query params would 422.
+"""
+from pydantic import BaseModel, Field
+
+
+class CreateFileRequest(BaseModel):
+    path: str
+    content: str
+    overwrite: bool = False
+
+
+class ReadFileRequest(BaseModel):
+    path: str
+
+
+class UpdateFileRequest(BaseModel):
+    path: str
+    content: str
+
+
+class DeleteFileRequest(BaseModel):
+    path: str
+    recursive: bool = False
+
+
+class ListDirRequest(BaseModel):
+    path: str
+    recursive: bool = False
+    max_depth: int = Field(default=1, ge=0)
+
+
+class StatRequest(BaseModel):
+    path: str
+
+
+class SearchRequest(BaseModel):
+    path: str
+    pattern: str
+    recursive: bool = True
+
+
+class MoveRequest(BaseModel):
+    src: str
+    dst: str
+    overwrite: bool = False
+
+
+class CopyRequest(BaseModel):
+    src: str
+    dst: str
+    overwrite: bool = False