script: add BIP360 P2MR validation, policy plumbing, and tests #35108

Adds draft BIP360 P2MR wiring across validation/policy/type handling and test coverage.

Changes in scope:

• witness v2 P2MR validation path in script interpreter
• policy/standardness handling for P2MR spends
• script type plumbing updates for WITNESS_V2_P2MR
• functional test feature_p2mr.py plus related unit test updates

Tested:

• ctest --output-on-failure -j6
• targeted functional tests including feature_p2mr.py, feature_taproot.py, and mempool package tests
• test_runner.py --extended --jobs=6
• compatibility/tool tests requiring extra build/release artifacts

♻️ Automatically closing for now based on heuristics. Please leave a comment, if this was erroneous. Generally, please focus on creating high-quality, original content that demonstrates a clear understanding of the project's requirements and goals.

📝 Moderators: If this is spam, please replace the title with ., so that the thread does not appear in search results.

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Reviews

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LLM Linter (✨ experimental)

Possible places where named args for integral literals may be used (e.g. func(x, /*named_arg=*/0) in C++, and func(x, named_arg=0) in Python):

• AddCoins(coins, CTransaction{tx_create}, 0, false) in src/test/transaction_tests.cpp
• AddCoins(coins, CTransaction{tx_create}, 0, false) in src/test/transaction_tests.cpp

^{2026-04-18 14:37:21}

This appears to be an automated false positive.

This PR is a tested, single-commit technical change (BIP360 P2MR wiring in interpreter/policy/type handling + tests), not spam content.

Could a maintainer please review and reopen for normal code review? I can immediately split this into smaller PRs if preferred.