feat(cco): add fabric handle support for gfx1250

[kawhil-amd]

Summary

• Add fabric handle support to CCO P2P memory sharing, following RCCL's pattern
• When the HIP runtime supports fabric handles (hipMemHandleTypeFabric, 0x8), CCO uses 64-byte opaque tokens exchanged via Allgather instead of dma-buf
  FDs passed through Unix sockets + SCM_RIGHTS
• Falls back transparently to the existing FD-based LocalBootstrapNetwork path when fabric is unavailable (runtime probe at ccoCommCreate)

Motivation

The current dma-buf FD exchange requires per-pair Unix domain socket setup (socket path construction, leader disambiguation, SCM_RIGHTS ancillary data).
Fabric handles reduce this to a single bootNet->Allgather of 64-byte tokens — simpler, faster, and required for upcoming gfx1250 / UALoE interconnect.

Changes

• include/mori/utils/hip_compat.hpp: Add hipMemFabricHandle_compat_t and hipMemHandleTypeFabricCompat compat shim (uses native types when HIP_FABRIC_API
  is defined)
• include/mori/cco/cco.hpp: Add ccoFabricHandle_t, change AllocMeta to union of shareFd/fabricHandle with isFabric flag, add handleType to ccoComm
• src/cco/cco_init.cpp:
  • ccoCommCreate: probe fabric support (alloc + export test), set handleType
  • ccoMemAlloc: use probed handle type for allocation and export
  • ccoWindowRegister: fabric path uses Allgather + hipMemImportFromShareableHandle; FD path unchanged as fallback. RDMA MR uses
    RegisterRdmaMemoryRegionAuto (ibv_reg_mr) in fabric mode
  • ccoMemFree/ccoCommDestroy: skip close(fd) when using fabric handles