Gate MoE fusion passes to XeLP+ and align pipeline comments

[Copilot]

Details:

• Problem summary: The MoE fusion block in transformations_pipeline.cpp needed to execute conditionally by GPU architecture, and nearby comments no longer matched the gated behavior.
• Behavior change (MoE fusion gating): Restrict MoeOpFusion, FuseMOESharedExpert, and FuseMOE3GemmCompressed registration to xe_lp and newer.
• Documentation-in-code update: Clarified comments to distinguish always-on MoE conversion passes from XeLP+-only MoE fusion passes.
• Snippet:

  if (!disable_moe_opt && device_info.arch >= cldnn::gpu_arch::xe_lp) {
      const bool has_batch_dim = !is_pa;
      manager.register_pass<ov::pass::MoeOpFusion>(has_batch_dim);
      manager.register_pass<ov::intel_gpu::FuseMOESharedExpert>();
      manager.register_pass<ov::intel_gpu::FuseMOE3GemmCompressed>();
  }

Tickets:

• N/A

AI Assistance:

• AI assistance used: yes
• AI was used to implement the conditional guard and update surrounding comments; human validation was performed via code review of the affected section and consistency checks against nearby transformation-pipeline logic.