Add fs implementation and add to trove

trovedb/trove.py

@@ -4,6 +4,10 @@ from pathlib import PurePosixPath
 
 NODE_ROOT_ID = 1
 
+class BadNoteType(TypeError):
+    """Raised when an invalid note type is encountered."""
+
+
 @runtime_checkable
 class Note(Protocol):
     """
@@ -47,6 +51,14 @@ class Tree(Protocol):
         """Create a new Tree with the given name."""
         ...
 
+    def rmdir(self, name: str) -> None:
+        """Remove a directory from the tree."""
+        ...
+
+    def child(self, name: str) -> Note:
+        """Retrieve a child not by name."""
+        ...
+
     def list(self) -> dict[str, int]:
         """Return all entries as {name: object_id}."""
         ...