fix(tma): select CTA-local G2S on SM120/SM121

[lucifer1004]

What this changes

Select CTA-local TMA global-to-shared loads on SM120/SM121, including their a and f targets. For local destinations, this avoids the compatibility call that conflicts with register reallocation. Partially addresses #1238.

Shape of the change

• Select local inline PTX for non-multicast loads of ranks 1–5.
• Retain the cluster route for other targets and multicast operations.
• Reject explicitly cluster-addressed destinations on the local route.
• Fix the target hint before lowering so automatic and explicit target selection agree.

SM120 local load -> direct TMA instruction -> register reallocation retained

Validation

• Target/rank controls and native, real NVVM and ptxas checks passed.
• Valid local GPU examples passed memory and synchronization checks.
• SM121 hardware and peer-CTA operations were not exercised.

Remaining work

The existing API permits cluster-shared memory. A GPU target alone does not prove that the destination and barrier belong to the executing CTA (thread block), and a helper call can carry these addresses through a generic pointer.

Prove locality for both operands or expose an explicit local API while preserving the cluster contract. The successful local controls do not resolve this API gap.

[nihalpasham]

Reviewed 5620feea: changes requested.

• The local path removes the compatibility call and retains register reallocation; rank/target controls and local GPU memory/synchronization checks pass.
• The existing API permits cluster-shared destinations. A GPU target alone does not prove that both destination and barrier belong to the executing CTA (thread block).

same GPU target:
  local destination + barrier -> CTA form is valid
  peer-CTA destination        -> preserve the cluster contract

• Establish locality or introduce an explicit local API. Checking only explicitly cluster-typed pointers misses generic pointers across helper calls. Cover both operands and preserve existing cluster behavior.
• Rebase and sign the revision.

#1238 remains partial.