docs: add getting-started walkthrough

Author: sahilgundu

docs/getting-started.md

@@ -0,0 +1,24 @@
+# Getting Started (patterns-only)
+
+This repo is sanitized (no client code/data). Use this mini flow to **see the patterns**.
+
+## Prereqs
+- BigQuery **Sandbox** (free) in your Google account
+- Cloud Shell or local `bq` CLI (optional for the load step)
+
+---
+
+## 1) Create a demo dataset + table (DDL)
+
+```sql
+CREATE SCHEMA IF NOT EXISTS fx_demo;
+
+CREATE TABLE IF NOT EXISTS fx_demo.events (
+  ts   TIMESTAMP,
+  pair STRING,
+  px   NUMERIC,
+  qty  INT64,
+  src  STRING
+)
+PARTITION BY DATE(ts)
+CLUSTER BY pair;