[rearden-grok]

Fixes #1227.

gettxout returned a mempool coin before checking spends_outpoint. A confirmed output spent in the mempool already came back null. The parent-then-child chapter of rpc_regtest_mature_chain_ops now pins both.

#1191 carries the same gettxout hunk inside a larger RPC bundle. Drop that commit when rebasing #1191.

Local cargo test -p rbitcoin-rpc --test suite rpc_regtest_mature_chain_ops went red on the new assert, then green. cargo fmt, clippy, cargo deny, and ast-grep passed. Workspace cargo test was not run on this host.

[rearden-grok]

0 bugs, 0 suggestions, 0 nits.

Summary

gettxout now returns null on the unconfirmed branch when MempoolHub::spends_outpoint finds a live mempool spender, using the same (Txid, vout) conflict-map lookup the confirmed branch already uses. That map is filled for every input of a live mempool tx, so a child spending a mempool parent is hidden when include_mempool is true; include_mempool false never consults the mempool, and an unconfirmed out is already null. REST getutxos calls gettxout, Electrum listunspent already skipped mempool-spent outs, and scantxoutset / gettxoutsetinfo are unsupported. The journey submits a child that spends parent vout 0, expects null for both include_mempool values, and still requires the unspent child output at confirmations 0. Help text, docs/rpc.md, and the changelog fragments match that coins view.

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