fix(dcp): support disposable A2A channel profiling

[FujitsuPolycom]

Summary

• add opaque channel checkpoints to PCIeDCPA2APool
• restore the exact pre-profile channel and alias map after disposable capture
• close only channels created after the checkpoint
• reject cross-pool checkpoints and lifecycle calls during active capture

This supplies the lifecycle contract used by vLLM's disposable DCP A2A memory
profiling without leaking profiling-only IPC allocations into the serving pool.

Sparkinfer rebase

The branch is based on local-inference-lab/sparkinfer@ec2cd4d and uses the
new sparkinfer.comm.pcie package layout. It does not restore the retired
b12x.distributed namespace.

Validation

• focused lifecycle suite: 7 passed
• combined Sparkinfer integration suite: 56 passed, 4 GPU-gated skips
• Ruff and compileall: passed
• included in the exact v19 integration image used for the TP4/DCP4 model gate

Fork integration draft only. Nothing has been pushed to the upstream repository.

AI-assisted implementation under human direction; the diff and validation
results were reviewed before publication.

Design document

GLM-5.2 Sparse CKV under Decode Context Parallelism is the canonical architecture, transport-contract, validation, and upstream-decomposition reference for this PR stack.