[ET-VK][ops] Add eq.Scalar operator

[SS-JIA]

Stack from ghstack (oldest at bottom):

• -> [ET-VK][ops] Add eq.Scalar operator #20383
• [ET-VK][ops] Add bitwise_or / logical_or operators #20382
• [ET-VK][patterns] Fuse torchao 4-bit quantized embedding to embedding_q4gsw #20381
• [ET-VK][quantized] Store dq8ca per-token zero-point as fp32 #20491

Adds Vulkan support for aten.eq.Scalar. This is the second of two ops needed to collapse the Llama4-mini TISO en_US backbone export to a single Vulkan partition (after bitwise_or): the discrete-speech mask compares the int token-id tensor against scalar constants via aten.eq.Scalar, which previously had no Vulkan implementation and forced a CPU fallback that split the delegated graph.

Implemented by extending the existing tensor-scalar binary-op path with a comparison-output variant: binary_scalar_buffer.glsl / binary_scalar_texture.glsl gain an IS_COMPARISON_OP code path that writes a uint8 (bool) output while leaving the existing arithmetic (e.g. pow) path unchanged; binary_scalar_buffer.yaml / binary_scalar_texture.yaml add an eq_scalar variant (half/float/int32 — the texture variant uses equal(X, Y) for per-lane bvec4, the buffer variant uses scalar X == Y); BinaryScalarOp.cpp adds an eq_tensor_scalar dispatch and VK_REGISTER_OP(aten.eq.Scalar, eq_tensor_scalar); op_registry.py registers aten.eq.Scalar OpFeatures (FP/INT tensor input, bool output). The int64 token tensor is serialized to int32 via the existing downcast_64_bit path, so the dispatch resolves to the int32 shader variant; no dtype-conversion pass is added.

This change was authored with Claude.

Differential Revision: D108457791

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❌ 5 New Failures, 3 Unrelated Failures

As of commit 05e3da6 with merge base 1621fa2 ():

NEW FAILURES - The following jobs have failed:

• pull / test-arm-backend-no-driver (test_pytest_ops_tosa) / linux-job (gh)
  RuntimeError: Command docker exec -t 9ab439edb6471aaab02287764e2c994aef7ba3b29784ee09dfb620ea217b6d2d /exec failed with exit code 1
• pull / test-qnn-models-linux (dl3) / linux-job (gh)
  RuntimeError: Command docker exec -t fa7de0b2867f3828e51f1f68db8bf7c0e343e991e67adaa4fea16dcbb0a6fcd0 /exec failed with exit code 92
• pull / test-static-llama-qnn-linux (stories_260k_bc) / linux-job (gh)
  RuntimeError: Command docker exec -t 1ae483cb657eb4d637fe0d08b7e36062668c7be8ae7d9d4ea737ae44e9f0826c /exec failed with exit code 92
• pull / unittest / linux / linux-job (gh)
  RuntimeError: Command docker exec -t 1315da9840a85ff36f988436844da0f706830499d02cf04b1f9eb4252b3e7dc8 /exec failed with exit code 1
• pull / unittest-editable / linux / linux-job (gh)
  RuntimeError: Command docker exec -t 23759b5f07c578939c1342100a689955c6266716eb70dc59a83bba4c369f08a7 /exec failed with exit code 1

BROKEN TRUNK - The following jobs failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / test-llama-runner-qnn-linux (fp32, qnn_16a16w, qnn) / linux-job (gh) (trunk failure)
• pull / unittest / macos / macos-job (gh) (trunk failure)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 1
• pull / unittest-editable / macos / macos-job (gh) (trunk failure)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 1

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