fix(pd): shape send list by swap count

[njzjz-bot]

Closes #5659.

Summary

• pack exactly one Paddle communication send-list pointer address per MPI swap
• reshape send_list from the packed pointer-array length (nswap) instead of sum(sendnum)
• keep send_num as the independent per-swap atom count consumed by the border communication op
• add a regression with nswap=2 and sendnum={3,4} so pointer-array length cannot be confused with the seven total sent atoms

Why existing tests missed this

The universal Paddle fixture uses an SE(A) model without message passing, so DeepPotPD never constructs communication tensors. The Paddle LAMMPS MPI case is skipped and uses the same non-message-passing model. Existing send-list tests covered NULL-atom remapping and send/receive counts, while the Paddle input specification accepts a dynamic send_list length; none asserted that the pointer-address tensor contains one entry per swap.

Validation

• ruff format .
• ruff check .
• clang-format --dry-run --Werror on all changed C++ files
• built runUnitTests_cc
• TestRemapCommSendlist.*: 5 passed, including the nswap != sum(sendnum) regression

The local environment does not include the Paddle inference SDK, so the Paddle-enabled compile/integration job is left to CI.

Coding agent: Codex
Codex version: codex-cli 0.144.4
Model: gpt-5.6-sol
Reasoning effort: xhigh

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.32%. Comparing base (6c3b985) to head (5af9aa5).

Files with missing lines	Patch %	Lines
source/api_cc/src/DeepPotPD.cc	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5850      +/-   ##
==========================================
- Coverage   78.58%   78.32%   -0.26%     
==========================================
  Files        1050     1050              
  Lines      120637   120643       +6     
  Branches     4356     4356              
==========================================
- Hits        94801    94497     -304     
- Misses      24278    24579     +301     
- Partials     1558     1567       +9     

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[njzjz]

Possible reviewers based on changed lines, exact file history, and exact-file review history:

• @wanghan-iapcm — 11 commits on changed files; 35 reviews on exact changed files (source/api_cc/include/common.h, source/api_cc/src/DeepPotPD.cc, source/api_cc/src/common.cc).
• @OutisLi — 16 reviews on exact changed files (source/api_cc/include/common.h, source/api_cc/src/common.cc).

No review request was made automatically.

Coding agent: Codex
Codex version: codex-cli 0.144.4
Model: gpt-5.6-sol
Reasoning effort: xhigh