feat(gateway): support per-channel and per-session queue policy overrides

src/gateway/lane-queue.test.ts

@@ -248,4 +248,23 @@ describe('LaneQueue', () => {
     await expect(p1).resolves.toBe('active');
     await expect(p3).resolves.toBe('new-pending');
   });
+
+  it('supports per-enqueue policy overrides', async () => {
+    const queue = new LaneQueue({ mode: 'collect', cap: 10, overflow: 'drop_old' });
+    let resolveFirst!: () => void;
+    const firstBlocks = new Promise<void>((r) => { resolveFirst = r; });
+
+    const p1 = queue.enqueue('lane-a', async () => {
+      await firstBlocks;
+      return 'active';
+    });
+    const p2 = queue.enqueue('lane-a', async () => 'old-pending', { mode: 'steer' });
+    const p3 = queue.enqueue('lane-a', async () => 'latest-pending', { mode: 'steer' });
+
+    await expect(p2).rejects.toThrow('Superseded by newer request');
+    resolveFirst();
+
+    await expect(p1).resolves.toBe('active');
+    await expect(p3).resolves.toBe('latest-pending');
+  });
 });