pnnx fuse adjacent permute, eliminate noop permute

[nihui]

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[Copilot]

Pull request overview

This PR implements a new optimization pass to fuse adjacent permute and transpose operations in the PNNX tool, reducing redundant dimension reordering operations in neural network graphs.

Key Changes:

• Added fuse_adjacent_permute optimization pass that combines consecutive Tensor.permute and torch.transpose operations into a single permute operation
• Integrated the new pass into the level 5 optimization pipeline
• Added comprehensive test coverage with multiple permute/transpose chains

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tools/pnnx/src/pass_level5/fuse_adjacent_permute.h	Header file declaring the new fuse_adjacent_permute function
tools/pnnx/src/pass_level5/fuse_adjacent_permute.cpp	Implementation of the permute fusion algorithm that composes multiple permutation operations
tools/pnnx/src/pass_level5.cpp	Integration of the new pass into the level 5 optimization pipeline
tools/pnnx/src/CMakeLists.txt	Added the new source file to the build configuration
tools/pnnx/tests/test_pnnx_fuse_adjacent_permute.py	Test file with multiple test cases exercising adjacent permute fusion
tools/pnnx/tests/CMakeLists.txt	Added the new test to the test suite

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[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

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