[op] integer tensor basics

[samthakur587]

Parent: #15

Op / kernel

integer tensor basics

Support Bool/Int64 for masks, indices, and arange outputs.

Acceptance criteria

• ATen / custom op registered on PrivateUse1
• Host (CPU sim) implementation
• OpenCL kernel + runtime launch (or explicit deferral note)
• Test vs CPU reference in tests/
• Linked PR closes this issue

Category

cat-dtype