chore: drop the core to 0.1.0 and restate the stability promise

The API has one set of consumers and no outside users, so declaring 1.0.0
with a stability guarantee was premature. Until 1.0.0 any minor bump may
reshape the API; the written guarantee starts there. Plugins pin 0.1.0.

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "nemo-repo-core"
-version = "1.0.0"
+version = "0.1.0"
 description = "Shared foundation for repository-aware Nemo file manager plugins"
 readme = "README.md"
 requires-python = ">=3.8"