Integrate FastMCP

This commit integrates FastMCP, a high-level MCP server implementation originally written by Jeremiah Lowin,
into the official MCP SDK. It also updates dependencies and adds new dev dependencies.
It moves the existing SDK into a .lowlevel .

tests/server/fastmcp/resources/test_file_resources.py

@@ -0,0 +1,115 @@
+import os
+
+import pytest
+from pathlib import Path
+from tempfile import NamedTemporaryFile
+from pydantic import FileUrl
+
+from mcp.server.fastmcp.resources import FileResource
+
+
+@pytest.fixture
+def temp_file():
+    """Create a temporary file for testing.
+
+    File is automatically cleaned up after the test if it still exists.
+    """
+    content = "test content"
+    with NamedTemporaryFile(mode="w", delete=False) as f:
+        f.write(content)
+        path = Path(f.name).resolve()
+    yield path
+    try:
+        path.unlink()
+    except FileNotFoundError:
+        pass  # File was already deleted by the test
+
+
+class TestFileResource:
+    """Test FileResource functionality."""
+
+    def test_file_resource_creation(self, temp_file: Path):
+        """Test creating a FileResource."""
+        resource = FileResource(
+            uri=FileUrl(temp_file.as_uri()),
+            name="test",
+            description="test file",
+            path=temp_file,
+        )
+        assert str(resource.uri) == temp_file.as_uri()
+        assert resource.name == "test"
+        assert resource.description == "test file"
+        assert resource.mime_type == "text/plain"  # default
+        assert resource.path == temp_file
+        assert resource.is_binary is False  # default
+
+    def test_file_resource_str_path_conversion(self, temp_file: Path):
+        """Test FileResource handles string paths."""
+        resource = FileResource(
+            uri=FileUrl(f"file://{temp_file}"),
+            name="test",
+            path=Path(str(temp_file)),
+        )
+        assert isinstance(resource.path, Path)
+        assert resource.path.is_absolute()
+
+    async def test_read_text_file(self, temp_file: Path):
+        """Test reading a text file."""
+        resource = FileResource(
+            uri=FileUrl(f"file://{temp_file}"),
+            name="test",
+            path=temp_file,
+        )
+        content = await resource.read()
+        assert content == "test content"
+        assert resource.mime_type == "text/plain"
+
+    async def test_read_binary_file(self, temp_file: Path):
+        """Test reading a file as binary."""
+        resource = FileResource(
+            uri=FileUrl(f"file://{temp_file}"),
+            name="test",
+            path=temp_file,
+            is_binary=True,
+        )
+        content = await resource.read()
+        assert isinstance(content, bytes)
+        assert content == b"test content"
+
+    def test_relative_path_error(self):
+        """Test error on relative path."""
+        with pytest.raises(ValueError, match="Path must be absolute"):
+            FileResource(
+                uri=FileUrl("file:///test.txt"),
+                name="test",
+                path=Path("test.txt"),
+            )
+
+    async def test_missing_file_error(self, temp_file: Path):
+        """Test error when file doesn't exist."""
+        # Create path to non-existent file
+        missing = temp_file.parent / "missing.txt"
+        resource = FileResource(
+            uri=FileUrl("file:///missing.txt"),
+            name="test",
+            path=missing,
+        )
+        with pytest.raises(ValueError, match="Error reading file"):
+            await resource.read()
+
+    @pytest.mark.skipif(
+        os.name == "nt", reason="File permissions behave differently on Windows"
+    )
+    async def test_permission_error(self, temp_file: Path):
+        """Test reading a file without permissions."""
+        temp_file.chmod(0o000)  # Remove all permissions
+        try:
+            resource = FileResource(
+                uri=FileUrl(temp_file.as_uri()),
+                name="test",
+                path=temp_file,
+            )
+            with pytest.raises(ValueError, match="Error reading file"):
+                await resource.read()
+        finally:
+            temp_file.chmod(0o644)  # Restore permissions