Add tests for backtest-client getAssets and createOrder unknown symbol

Covers the two remaining uncovered lines: getAssets returning all
symbols from bar data, and createOrder throwing on unknown symbols.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/backtest-client.test.ts

@@ -150,6 +150,17 @@ describe('BacktestClient', () => {
         });
     });
 
+    describe('getAssets', () => {
+        it('returns all symbols from bar data', async () => {
+            const assets = await client.getAssets({ status: 'active', asset_class: 'us_equity' });
+            const symbols = assets.map(a => a.symbol);
+            expect(symbols).toEqual(['QQQ', 'TQQQ', 'SQQQ']);
+            expect(assets[0].status).toBe('active');
+            expect(assets[0].asset_class).toBe('us_equity');
+            expect(assets[0].fractionable).toBe(true);
+        });
+    });
+
     describe('getAsset', () => {
         it('returns asset info', async () => {
             const asset = await client.getAsset('TQQQ');
@@ -157,4 +168,16 @@ describe('BacktestClient', () => {
             expect(asset.fractionable).toBe(true);
         });
     });
+
+    describe('createOrder - unknown symbol', () => {
+        it('throws when no bar data exists', async () => {
+            await expect(client.createOrder({
+                symbol: 'AAPL',
+                notional: 1000,
+                side: 'buy',
+                type: 'market',
+                time_in_force: 'day',
+            })).rejects.toThrow('No bar data for AAPL');
+        });
+    });
 });