feat(gateway): expose context usage and warning events

src/gateway/protocol.test.ts

@@ -308,5 +308,30 @@ describe('protocol', () => {
         data,
       });
     });
+
+    it('creates a context warning event message', () => {
+      const data = {
+        level: 'warning',
+        message: 'Context usage is 76.0%',
+        budget: {
+          estimatedTokens: 76000,
+          contextWindow: 100000,
+          remainingTokens: 24000,
+          usagePct: 76,
+          thresholdPct: 80,
+          thresholdTokens: 80000,
+          shouldCompact: false,
+        },
+        actions: {
+          checkpointSaved: false,
+          autoCompacted: false,
+        },
+      };
+      expect(makeEvent(3, 'context_warning', data)).toEqual({
+        id: 3,
+        event: 'context_warning',
+        data,
+      });
+    });
   });
 });