chore: import upstream snapshot with attribution

tests/fixtures/sample.sql

@@ -0,0 +1,37 @@
+-- Sample SQL fixture for code-review-graph parser tests
+
+CREATE TABLE users (
+    id       INTEGER PRIMARY KEY,
+    name     TEXT    NOT NULL,
+    email    TEXT    UNIQUE
+);
+
+CREATE TABLE orders (
+    id         INTEGER PRIMARY KEY,
+    user_id    INTEGER REFERENCES users(id),
+    total      NUMERIC(10, 2),
+    created_at TIMESTAMP DEFAULT NOW()
+);
+
+CREATE VIEW active_orders AS
+    SELECT o.id, u.name, o.total
+    FROM orders o
+    JOIN users u ON u.id = o.user_id
+    WHERE o.total > 0;
+
+CREATE FUNCTION get_user_total(p_user_id INTEGER)
+RETURNS NUMERIC AS $$
+    SELECT SUM(total)
+    FROM orders
+    WHERE user_id = p_user_id;
+$$ LANGUAGE sql;
+
+CREATE OR REPLACE PROCEDURE archive_old_orders(cutoff_date DATE)
+LANGUAGE plpgsql AS $$
+BEGIN
+    INSERT INTO orders_archive
+    SELECT * FROM orders WHERE created_at < cutoff_date;
+
+    DELETE FROM orders WHERE created_at < cutoff_date;
+END;
+$$;