Add local pipeline demo launcher

coordinator/README.md

@@ -91,6 +91,24 @@ to inspect a bounded first page of a partial or completed final result before
 downloading it. The UI never exposes source datasets or shard inputs; partial
 CSVs remain available only as diagnostics.
 
+### One-command manual demo
+
+From the repository root, create the Python environment once, then start a
+self-contained UI demo with two local reference workers:
+
+```sh
+python3 -m venv .venv
+.venv/bin/pip install -e '.[dev]'
+make demo-ui
+```
+
+This uses a separate Docker project and ports `18080` (coordinator) and
+`55432` (PostgreSQL), so it does not conflict with the normal stack. Open
+`http://localhost:18080/ui`, use username `operator` and password
+`demo-ui-secret`, upload a small ChEMBL TSV, and observe the workers process
+it. Change the worker count with `make demo-ui DEMO_WORKERS=3`; stop all demo
+services and workers with `make demo-down`.
+
 `up` starts three services in order: Postgres waits until `pg_isready` passes, a
 one-shot `migrate` container applies the schema and exits, and only then does the
 coordinator start — so it never queries a database that has no tables.