Fix: Wrong handle in multi-stream handle test (#186)

The multi-stream handle test failed flakily on a recent CI run on
`main`:
https://github.com/iree-org/fusilli/actions/runs/22334529677/job/64623964052

```
-------------------------------------------------------------------------------
Handle creation with stream and deviceId
  Create multiple handles with different HIP streams
-------------------------------------------------------------------------------
/workspace/tests/hip_tests/test_handle.cpp:92
...............................................................................

/workspace/tests/hip_tests/test_handle.cpp:136: FAILED:
  REQUIRE( readData == hostData )
with expansion:
  { 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.
  0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f,
  0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f }
  ==
  { 3.14f, 3.14f, 3.14f, 3.14f, 3.14f, 3.14f, 3.14f, 3.14f, 3.14f, 3.14f, 3.
  14f, 3.14f, 3.14f, 3.14f, 3.14f, 3.14f, 3.14f, 3.14f, 3.14f, 3.14f, 3.14f, 3.
  14f, 3.14f, 3.14f, 3.14f, 3.14f, 3.14f, 3.14f, 3.14f, 3.14f, 3.14f, 3.14f }

terminate called after throwing an instance of 'std::bad_variant_access'
  what():  std::get: wrong index for variant
/workspace/tests/hip_tests/test_handle.cpp:136: FAILED:
  {Unknown expression after the reported line}
due to a fatal error condition:
  SIGABRT - Abort (abnormal termination) signal
```
- Fixed copy-paste bug in `test_handle.cpp` where the "Create multiple
handles with different HIP streams" test was using `handle1` instead of
`handle2` for the second buffer's `allocate` and `read` calls
- (I'm not sure if this is accurate) This could have caused a
cross-stream race condition resulting in flaky D2H reads returning all
zeros instead of the expected `3.14f` values

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Signed-off-by: Sambhav Jain <sambhav@alumni.stanford.edu>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: sjain-stanford

tests/hip_tests/test_handle.cpp

@@ -130,9 +130,9 @@ TEST_CASE("Handle creation with stream and deviceId", "[handle][hip_tests]") {
 
     // Verify we can allocate, write, and read buffers on handle2
     FUSILLI_REQUIRE_ASSIGN(Buffer deviceBuffer2,
-                           Buffer::allocate(handle1, bufferShape, hostData));
+                           Buffer::allocate(handle2, bufferShape, hostData));
     readData.clear();
-    FUSILLI_REQUIRE_OK(deviceBuffer2.read(handle1, readData));
+    FUSILLI_REQUIRE_OK(deviceBuffer2.read(handle2, readData));
     REQUIRE(readData == hostData);
 
     // Clean up.