feat(docs): update README to reflect JSON-LD conversion implementation

- mark task 04 as implemented in the project overview
- add convert_json.py as the entry script for task 04
- clarify output paths for JSON-LD conversion artifacts

README.md

@@ -60,7 +60,7 @@ machine (no parallel work). Every task writes a completion marker
 | 01 Lab configuration | `make_lab_config.py` | `out/config/lab_config.yaml` | implemented |
 | 02 Process flow diagrams | `make_process_flow.py` | `out/report/process_flow.md`, `out/report/diagrams/` | implemented |
 | 03 CSV data generation | `generate_data.py` | `out/csv/` tree + `MANIFEST.csv` | implemented |
-| 04 Convert to JSON-LD | `convert_json.py` | `out/json/full/`, `out/json/hybrid/dataset.jsonld` | planned |
+| 04 Convert to JSON-LD | `convert_json.py` | `out/json/full/`, `out/json/hybrid/dataset.jsonld` | implemented |
 | 05 Convert to SQLite | `convert_sqlite.py` | `out/sqlite/tribo.db` | planned |
 | 06 Convert to PostgreSQL | `convert_postgresql.py` | live `tribo` DB + `out/pg/tribo.dump` | planned |
 | 07 Convert to RDF | `convert_rdf.py` | `out/rdf/dataset.nt.gz`, oxigraph store | planned |
@@ -145,9 +145,11 @@ docs/
   examples/     imported reference materials (not binding)
 out/            ALL generated artifacts (git-ignored, reproducible):
   config/ csv/ json/ sqlite/ pg/ rdf/ bench/ report/ .done/
+common/               shared helpers (storage_sizes.csv contract, ...)
 make_lab_config.py    task 01 entry script (one script per task, repo root)
 make_process_flow.py  task 02 entry script
 generate_data.py      task 03 entry script
+convert_json.py       task 04 entry script
 requirements.txt      closed dependency list (docs/rules/code-python-style.md)
 ```