feat(wasm-utxo): add BitGoPsbt.combineInputs for raw PSBT merge#299
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Adds `combine_inputs` (Rust/WASM) and `combineInputs` (JS/TS) to `BitGoPsbt`. This method merges all input fields from a raw PSBT (provided as bytes) into the current PSBT. Unlike `combineMusig2Nonces`, it handles all script types and works with stripped PSBTs: - Parses the source with bitcoin's base PSBT deserializer for non-ZEC coins; for ZEC uses a new `ZcashBitGoPsbt::deserialize_stripped` that applies the ZEC-aware transaction converter but skips the `ZecConsensusBranchId` proprietary-key requirement. - Dispatches on the `BitGoPsbt` enum variant so ZEC PSBTs are parsed correctly without requiring coin information at call sites. - Copies per input: partial_sigs, tap_key_sig, tap_script_sigs, proprietary. Used by ims-utxo to combine an HSM-signed response PSBT with the full request PSBT before verifying and finalizing the transaction. Tests cover BTC (p2shP2wsh), LTC, ZEC, and ZcashBitGoPsbt metadata in a consolidated `test/fixedScript/combineInputs.ts`. Refs: T1-3607
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davidkaplanbitgo
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Jun 18, 2026
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Summary
combine_inputs(Rust/WASM) andcombineInputs(JS/TS) toBitGoPsbtpartial_sigs,tap_key_sig,tap_script_sigs,proprietaryZcashBitGoPsbt::deserialize_stripped— uses the ZEC-aware transaction converter but skips theZecConsensusBranchIdrequirement, so stripped HSM responses are acceptedBitGoPsbtenum variant to avoid threading coin information through the calltest/fixedScript/combineInputs.ts: BTC (p2shP2wsh), LTC, ZEC (combine + finalize + extract, stripped response), ZcashBitGoPsbt metadataMotivation
After HSM co-signing, ims-utxo needs to merge the stripped HSM response PSBT back into the full request PSBT before verifying signatures and finalizing. The existing
combineMusig2Noncesonly handles MuSig2 proprietary data; this method handles all script types. The ZEC-aware parser path is needed becauseZcashBitGoPsbt::deserializerejects PSBTs lacking theZecConsensusBranchIdproprietary key, which stripped HSM responses may omit.Test plan
cargo testinpackages/wasm-utxopassesnpm testinpackages/wasm-utxopasses (17combineInputstests: BTC ×6, LTC ×1, ZEC ×5, ZcashBitGoPsbt metadata ×5)Refs: T1-3607