docs: update DEVELOPMENT.md and README.md for clarity and structure improvements

DEVELOPMENT.md

@@ -3,6 +3,7 @@
 Notes for contributors extending the exporter (new loaders/targets, schema tweaks, etc.). User-facing usage lives in `README.md`.
 
 ## Local environment
+
 - Install deps with `uv sync --dev`.
 - Run checks with `uv run pre-commit run --all-files`.
 - Add pre-commit to git hooks with `uv run pre-commit install`.
@@ -11,6 +12,7 @@ Notes for contributors extending the exporter (new loaders/targets, schema tweak
   - `NEPTUNE3_E2E_API_TOKEN`, `NEPTUNE3_E2E_PROJECT`
 
 ## Code structure (src/neptune_exporter)
+
 - `main.py`: Click CLI wiring for `export`, `load`, `summary`.
 - `exporters/`: `Neptune2Exporter` (neptune-client) and `Neptune3Exporter` (neptune-query); both yield `pyarrow.RecordBatch` objects matching `model.SCHEMA`.
 - `export_manager.py`: Orchestrates export per project/run, fans out batches per run, and skips runs already on disk.
@@ -22,13 +24,15 @@ Notes for contributors extending the exporter (new loaders/targets, schema tweak
 - `utils.py`: Shared helpers (`sanitize_path_part` adds a digest to keep paths safe/unique).
 
 ## Data flow overview
+
 1. Export (primary): exporter → `ExportManager` → `ParquetWriter` (+ file downloads). A run is considered complete when `*_part_0.parquet` exists; runs without it are rewritable.
 2. Summary: `ParquetReader` → `SummaryManager` → `ReportFormatter`.
 3. Load (optional): `ParquetReader` → `LoaderManager` → selected `DataLoader`.
 
 Exports are resumable but not incremental: reruns skip completed runs, so new data added to an already-exported run will be missed unless you re-export to a fresh location.
 
 ## Adding or changing components
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 - **New loader** (e.g., another tracking backend):
   - Implement `DataLoader` methods (`create_experiment`, `find_run`, `create_run`, `upload_run_data`).
   - Handle attribute name sanitization and step conversion internally; `loader_manager` provides `step_multiplier` (keep it consistent when Neptune steps are floats).
@@ -43,12 +47,14 @@ Exports are resumable but not incremental: reruns skip completed runs, so new da
 - **File handling**:
   - Artifacts are stored under `--files-path/<sanitized_project_id>/...`; keep the relative paths in `file_value.path` stable so loaders can find the payloads.
 - **Forking**:
-  - Fork metadata exists only in Neptune 3.x exports. W&B supports forks only in a limited/preview fashion—avoid relying on strict fidelity. MLflow does not support forking and saves parents as tags instead. 
+  - Fork metadata exists only in Neptune 3.x exports. W&B supports forks only in a limited/preview fashion — avoid relying on strict fidelity. MLflow does not support forking and saves parents as tags instead.
 
 ## Testing notes
+
 - Prefer function-style pytest tests (no classes) and `unittest.mock.Mock` for doubles.
 - Look at `tests/test_storage.py` and `tests/test_summary_manager.py` for patterns.
 - When adding loader/exporter behavior, add small, focused tests around boundary cases (empty batches, missing metadata, bad attribute names).
 
 ## CI
+
 GitHub Actions runs linting (ruff, mypy, license headers) and tests on Python 3.13 using uv. Workflows live in `.github/workflows/ci.yml`.