remove notebooks

- Delete notebooks/ (personal scratch artifacts; gitignored)
- Move nbformat to --extra migrate; lazy imports in migrate.py and
  cli.py so base CLI loads without it
- Restore langchain-text-splitters in core (chunking dependency)

CHANGELOG.md

@@ -13,7 +13,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `kg_ocr.embeddings.config_loader.KgConfig` for traversal tunables and Neo4j credentials from env.
 - `kg_ocr.export`: node-link JSON (lossless round-trip), GraphML for Gephi/Cytoscape, and batched MERGE export to Neo4j via `Neo4jExporter`.
 - CLI: `ocr-pipeline kg build|stats|query|export` subcommands with lazy kg_ocr imports.
-- Optional extras: `kg` (networkx + txtai + litellm + python-dotenv), `neo4j` (driver).
+- Optional extras: `kg` (networkx + txtai + litellm + python-dotenv), `neo4j` (driver), `migrate` (nbformat).
 - `init` command: writes a minimal `config.yaml` with platform-correct defaults and checks for Tesseract.
 - `demo` command: runs the pipeline on a bundled sample screenshot, prints the output Markdown, and verifies the install in <30s.
 - `setup [basic|full]` command: executes install steps with confirmation (`--yes`/`--dry-run`).
@@ -46,6 +46,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Dead `src/ocr_pipeline/watch.py` shim (shadowed by the `watch/` package).
 - Stub `kg_ocr/cli/` directory (commands now in the main `ocr-pipeline` CLI).
 - Untracked `src/ocr_pipeline.egg-info` from git (still gitignored).
+- `notebooks/` (personal scratch artifacts; gitignored).
+- `nbformat` from core dependencies (moved to `migrate` extra).
 - Unused core dependencies: `tqdm`, `scikit-image`, `sqlite-utils`, `xxhash`, `python-slugify`, `python-magic`, `legacy-cgi`.
 - Core dependency on `spacy` (moved to `scientific` extra).
 - Core dependency on `paddleocr`/`paddlepaddle` (moved to `paddle` extra).