ext/ep: fix SWITCH_* macros and add missing standard headers

- Wrap SWITCH_* macros in launch.cuh in do { ... } while(false) so the
  trailing while(false) terminates the macro instead of dangling after
  the closing brace of the switch.
- Add #include <type_traits> to utils.cuh for std::remove_reference used
  in UNROLLED_WARP_COPY.
- Add #include <limits> to intranode_kernel.cu and internode.cu for
  std::numeric_limits.

Addresses Copilot review comments on PR #796.

src/ext/ep/kernels/internode.cu

@@ -1,5 +1,7 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
+#include <limits>
+
 #include "configs.cuh"
 #include "buffer.cuh"
 #include "exception.cuh"

src/ext/ep/kernels/intranode_kernel.cu

@@ -1,5 +1,7 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
+#include <limits>
+
 #include "configs.cuh"
 #include "buffer.cuh"
 #include "exception.cuh"

src/ext/ep/kernels/launch.cuh

@@ -19,45 +19,55 @@
 #endif
 
 #define SWITCH_RANKS(case_macro) \
-    switch (num_ranks) { \
-        case 2: case_macro(2); \
-        case 4: case_macro(4); \
-        case 8: case_macro(8); \
-        default: EP_HOST_ASSERT(false and "Unsupported ranks"); \
+    do { \
+        switch (num_ranks) { \
+            case 2: case_macro(2); \
+            case 4: case_macro(4); \
+            case 8: case_macro(8); \
+            default: EP_HOST_ASSERT(false and "Unsupported ranks"); \
+        } \
     } while (false)
 
 #define SWITCH_RDMA_RANKS(case_macro) \
-    switch (num_ranks / NUM_MAX_NVL_PEERS) { \
-        case 2: case_macro(2); \
-        case 3: case_macro(3); \
-        case 4: case_macro(4); \
-        case 8: case_macro(8); \
-        case 16: case_macro(16); \
-        case 18: case_macro(18); \
-        case 20: case_macro(20); \
-        default: EP_HOST_ASSERT(false and "Unsupported RDMA ranks"); \
+    do { \
+        switch (num_ranks / NUM_MAX_NVL_PEERS) { \
+            case 2: case_macro(2); \
+            case 3: case_macro(3); \
+            case 4: case_macro(4); \
+            case 8: case_macro(8); \
+            case 16: case_macro(16); \
+            case 18: case_macro(18); \
+            case 20: case_macro(20); \
+            default: EP_HOST_ASSERT(false and "Unsupported RDMA ranks"); \
+        } \
     } while (false)
 
 #define SWITCH_RANKS_WITH_DTYPE(dtype, case_macro) \
-    switch (num_ranks) { \
-        case 2: case_macro(dtype, 2); \
-        case 4: case_macro(dtype, 4); \
-        case 8: case_macro(dtype, 8); \
-        default: EP_HOST_ASSERT(false && "Unsupported ranks"); \
+    do { \
+        switch (num_ranks) { \
+            case 2: case_macro(dtype, 2); \
+            case 4: case_macro(dtype, 4); \
+            case 8: case_macro(dtype, 8); \
+            default: EP_HOST_ASSERT(false && "Unsupported ranks"); \
+        } \
     } while (false)
 
 #define SWITCH_TYPES(case_macro) \
-    switch (type) { \
-        case CUDA_R_16BF: case_macro(nv_bfloat16); \
-        case CUDA_R_32F:  case_macro(float); \
-        default: EP_HOST_ASSERT(false && "Unsupported type"); \
+    do { \
+        switch (type) { \
+            case CUDA_R_16BF: case_macro(nv_bfloat16); \
+            case CUDA_R_32F:  case_macro(float); \
+            default: EP_HOST_ASSERT(false && "Unsupported type"); \
+        } \
     } while (false)
 
 #define SWITCH_HIDDEN(case_macro) \
-    switch (hidden) { \
-        case 2560: case_macro(2560); \
-        case 4096: case_macro(4096); \
-        case 5120: case_macro(5120); \
-        case 7168: case_macro(7168); \
-        default: EP_HOST_ASSERT(false && "Unsupported hidden"); \
+    do { \
+        switch (hidden) { \
+            case 2560: case_macro(2560); \
+            case 4096: case_macro(4096); \
+            case 5120: case_macro(5120); \
+            case 7168: case_macro(7168); \
+            default: EP_HOST_ASSERT(false && "Unsupported hidden"); \
+        } \
     } while (false)

src/ext/ep/kernels/utils.cuh

@@ -2,6 +2,8 @@
 // Licensed under the MIT License.
 #pragma once
 
+#include <type_traits>
+
 #include "exception.cuh"
 
 #define UNROLLED_WARP_COPY(UNROLL_FACTOR, LANE_ID, N, DST, SRC, LD_FUNC, ST_FUNC) \