[do not merge] gosentry overflow-detection suppressions and run script

[AskAlexSharov]

Preserves the triage from running gosentry — a fork of the Go toolchain that panics on integer overflow/underflow at runtime — over the unit suite, the fuzz targets, and a syncing mainnet node. Not for merge: gosentry is not in CI, and these markers only earn their place if it becomes a recurring audit. Opened so the work is not lost.

The expensive part is not the code, it is knowing which sites are deliberate. Without this, the next instrumented run repeats the whole triage.

Two mechanisms, chosen by scope.

Packages that are modular arithmetic end to end are exempted wholesale in misc/gosentry-run.sh. Marking them in place does not scale — Sum128WithSeed alone has 16 arithmetic operations, 40 across the file:

-gcflags=github.com/erigontech/erigon/common/murmur3=-overflowdetect=false

Single benign sites inside packages worth instrumenting are marked in the source, so the rest of the package keeps its checks — the EVM is exactly where a real overflow would matter:

// overflow_false_positive
vByte := byte(vb.Uint64() - 27)

What was checked, and why each is benign.

site	why it wraps
murmur3, blake2b, recsplit.remix, ethash FNV	hash mixing; the reference C++ uses uint64_t, Rust ports spell it wrapping_mul
bitutil.Select, patricia.swarEdge, vm.codeBitmap	SWAR — the borrow out of a zero byte is the result
transaction_signing.go:421, contracts.go:335	v - 27; a wrapped value lands in 229–255 and TransactionSignatureIsValid accepts only 0 or 1
txn_executor.go:307	stNonce+1 < stNonce is itself the overflow check
vm/evm.go:233	documented in place: mod-2^64 subtraction is the correct computation
cache.go:245, cache_accessors.go:51	epoch 0 produces a garbage slot, rejected by the error path
prefix_trie.go, kvcache.go:241, nodedb.go:598, stage_senders.go:335	wrapped value is discarded, used as a map miss, or only reaches a debug log

Two real bugs came out of the same runs and are in their own PRs, not here: #23192 (AA gas limits summed unchecked; parseBitlist msb underflow) and #23173 (fuzz harness defects).

Notes

• misc/gosentry-run.sh has build, test and fuzz subcommands. The fuzz path sets RUSTFLAGS=-C link-arg=-lstdc++, without which the LibAFL harness fails to link against evmone's C++ modexp.
• Truncation detection (-truncationdetect=true) is deliberately not enabled: it fires within the first 1–4 executions of nearly every package and needs its own triage pass.
• common/murmur3 here also carries a wmul/wadd helper pair, kept as a worked example: two // overflow_false_positive markers silence all 40 sites because suppression survives inlining. The package exemption makes it redundant, and it diverges from the reference transcription, so it should probably be dropped before any merge. I did not measure whether the helpers are free — the benchmark run timed out.
• The exemption list is what lets a node start at all. Without it the node dies in seconds: first murmur3.go:41 via every index lookup, then recsplit.go:86.