Implement S3VersionStore::store_version_from_reader

.claude/CLAUDE.md

@@ -107,6 +107,7 @@ oxen push origin main               # Push to remote
 - When calling `get_staged_db_manager`, follow the doc comment on that function: drop the returned `StagedDBManager` as soon as possible (via a block scope or explicit `drop()`) to avoid holding the shared database handle longer than necessary.
 - When altering the `OxenError` enum, consider whether a hint needs to be added or updated in the `hint` method.
 - After changing any Rust code, verify that tests pass with the `bin/test-rust` script (not `cargo`). The script is documented in a comment at the top of its file.
+- Prefer using inline code over creating a new function when the function would only be called once and the function body would be less than 15 lines.
 
 # Testing Rules
 - Use the test helpers in `crates/lib/src/test.rs` (e.g., `run_empty_local_repo_test`) for unit tests in the lib code.