vulkan weight allocator prefer host memory fusion

[nihui]

No description provided.

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 34.48276% with 76 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.22%. Comparing base (0ed9702) to head (8f37497).

Files with missing lines	Patch %	Lines
src/allocator.cpp	33.91%	76 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6545      +/-   ##
==========================================
+ Coverage   93.18%   93.22%   +0.03%     
==========================================
  Files         847      847              
  Lines      266764   266744      -20     
==========================================
+ Hits       248591   248661      +70     
+ Misses      18173    18083      -90     

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[Copilot]

Pull request overview

This PR consolidates Vulkan “weights in host memory” handling by folding the former VkHostAllocator behavior into VkWeightAllocator, and wiring Net::load_model() to select host-memory preference via a flag rather than switching allocator classes.

Changes:

• Update Net::load_model() to construct VkWeightAllocator with a host-memory preference flag.
• Extend VkWeightAllocator to optionally allocate/import host-backed memory (and add cleanup for host pointers).
• Remove the exported VkHostAllocator class from the public allocator header and implementation.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
src/net.cpp	Switch allocator creation to a single VkWeightAllocator with host-memory preference.
src/allocator.h	Change VkWeightAllocator constructor signature; remove VkHostAllocator declaration.
src/allocator.cpp	Implement host-memory preference inside VkWeightAllocator; delete VkHostAllocator implementation.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

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