fix: stabilize logaddexp expression evaluation

[primorLee]

Summary

• evaluate expression logaddexp with the same numerically stable formulation used by the binary operator
• preserve IEEE-754 behavior for equal positive/negative infinities and propagate NaN operands
• classify non-finite values from their float bits so the checks remain valid in ncnn's Release build with -ffast-math
• add regressions for large finite operands and both equal-infinity cases

Tests

• Release build: cmake --build build-codex --target test_expression test_reshape test_crop test_interp -j 4
• ctest --test-dir build-codex -R '^test_(expression|reshape|crop|interp)$' --output-on-failure (4 passed)
• git diff --check

[tencent-adm]

All committers have signed the CLA.

[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: 47569bf67c

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[primorLee]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Chef's kiss.

Reviewed commit: 55dc6a9642

ℹ️ About Codex in GitHub

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