feat(cli): add featcopilot CLI for agentic usage

README.md

@@ -110,6 +110,39 @@ for feature, explanation in engineer.explain_features().items():
     print(f"{feature}: {explanation}")
 ```
 
+## Command-Line Interface
+
+FeatCopilot ships a `featcopilot` CLI for shell, scripting, and agentic
+(LLM tool-use) workflows — no Python glue required. All subcommands accept
+`--json` for machine-readable stdout; errors are written to stderr with a
+non-zero exit code so agents can parse failures deterministically.
+
+```bash
+# Discover capabilities (engines, selection methods, I/O formats)
+featcopilot info --json
+
+# Run feature engineering on a CSV / JSON file
+featcopilot transform \
+    --input data.csv --target label --output features.csv \
+    --engines tabular --max-features 50 --json
+
+# Inspect generated features (name, explanation, code) as JSON for an LLM
+featcopilot explain --input data.csv --target label
+
+# Equivalent module form
+python -m featcopilot info --json
+```
+
+Pass `--config config.json` to provide nested keys such as `llm_config`;
+explicit CLI flags override values from the config file.
+
+> **Parquet I/O.** FeatCopilot's base install does not pin a parquet engine.
+> To use `--input file.parquet` / `--output file.parquet` (or the
+> `parquet` value in `--input-format` / `--output-format`), install one of
+> `pyarrow` or `fastparquet`. `featcopilot info --json` reports
+> `"parquet_available": true` only when an engine is importable in the
+> current environment.
+
 ## Engines
 
 ### Tabular Engine

featcopilot/__main__.py

@@ -0,0 +1,6 @@
+"""Enable ``python -m featcopilot`` to dispatch to the CLI."""
+
+from featcopilot.cli import main
+
+if __name__ == "__main__":
+    raise SystemExit(main())