#216 - Fix engine lifecycle cleanup

[cliffburdick]

No description provided.

[greptile-apps]

Greptile Summary

This PR fixes engine lifecycle cleanup and reinitialization behavior. The main changes are:

• Releases the active engine on shutdown() and allows a later fresh init.
• Keeps DPDK dma-buf fds open until EAL cleanup completes.
• Adds base-engine memory-region deallocation.
• Adds RDMA and ibverbs MR deregistration during teardown.
• Documents the single-active-engine lifecycle in the API docs.

Confidence Score: 5/5

This looks safe to merge.

• No blocking issues found in the changed code.

Important Files Changed

Filename	Overview
src/engine_dpdk.cpp	Retains successful DPDK dma-buf fds and closes them after EAL cleanup.
src/common.cpp	Resets the active engine on shutdown and failed initialization.
src/engine.cpp	Adds base-engine cleanup for memory regions and retained fd state.
src/engine.h	Adds allocation ownership metadata and EngineFactory reset support.
src/engines/dpdk/daqiri_dpdk_engine.cpp	Resets DPDK quit state on init and tags HUGE allocations with their owner.
src/engines/ibverbs/daqiri_ibverbs_engine.cpp	Tracks ibverbs memory registrations and deregisters them before PD teardown.
src/engines/rdma/daqiri_rdma_engine.cpp	Cleans up partial RDMA MR registration failures and deregisters MRs before PD teardown.

_{Reviews (2): Last reviewed commit: "#216 - Retain DPDK dma-buf descriptors" | Re-trigger Greptile}