docs(gfql): engines page — orient the cold newcomer (where does g come from)

§0 newcomer user-test: a first-timer landing on engines.rst cold hit the headline
`g.gfql(query, engine='polars')` with no `g`/`query` defined (NameError on copy-paste);
construction was buried (inside the coercion warning + the bottom install block) and there
was no early pointer to getting-started. Add (1) an early "New to GFQL? build a graph first
-> :doc:`about`" note, and (2) a 2-line self-contained preamble (graphistry.edges + a query)
so the first example runs as-is. Reuses content already on the page; no restructure.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: lmeyerov

docs/source/gfql/engines.rst

@@ -8,6 +8,10 @@ the engine with one keyword — ``engine=``, accepted uniformly by ``g.gfql()``
 ``g.hop()`` — and GFQL returns **identical results** on every one (differential parity
 is a release gate). Pick the engine that fits your hardware and workload; nothing else changes.
 
+.. note::
+   **New to GFQL?** This page assumes you already have a graph ``g`` and a ``query``. If not,
+   build one first — see :doc:`about` (10 Minutes to GFQL).
+
 The one-line speedup
 --------------------
 
@@ -16,6 +20,10 @@ engine is a one-keyword change — no GPU, same results:
 
 .. code-block:: python
 
+   import graphistry
+   g = graphistry.edges(df, 'src', 'dst')   # df: your edges dataframe (pandas / Polars / cuDF)
+   query = "MATCH (a)-[e]->(b) RETURN b"     # any GFQL / Cypher query
+
    g.gfql(query)                    # engine='pandas' (default)
    g.gfql(query, engine='polars')   # up to ~38x faster on real graphs, no GPU, identical results