Add Venom consecutive ADD folding pass

[augmentcode]

Summary

• add ConsecutiveAddFoldingPass for single-use chained add instructions with compile-time constant operands
• wire the pass into O2/O3/Os pipelines and the algebraic-optimization disable flag
• add focused Venom pre/post tests for literal, assigned-constant, three-deep, zero-canceling, and multi-use cases

Tests

• SETUPTOOLS_SCM_PRETEND_VERSION=0.0.0 uv run pytest tests/unit/compiler/venom/test_consecutive_add_folding.py tests/unit/compiler/venom/test_algebraic_optimizer.py
• SETUPTOOLS_SCM_PRETEND_VERSION=0.0.0 uv run python - <<'PY' ... pass order validation ... PY
• SETUPTOOLS_SCM_PRETEND_VERSION=0.0.0 uv run black --check vyper/venom/passes/consecutive_add_folding.py tests/unit/compiler/venom/test_consecutive_add_folding.py

Notes

• This is a manual session, but the required github-api tool is not available here, so this PR was created with github-app-api.

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Pull Request opened by Augment Code | View session

[augmentcode]

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[augmentcode]

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