feat(wasm-utxo): add raw PSBT parser showing key-value structure

Implement a new parser module for examining low-level PSBT structure with
raw key-value pairs as defined in BIP-174. This exposes internal details
like proprietary keys, raw type IDs, and byte structure that standard
parsers might hide.

Also add test utilities for loading PSBT fixtures across different networks
and signature states.

Issue: BTC-2652

Co-authored-by: llm-git <[email protected]>

Author: OttoAllmendinger

packages/wasm-utxo/cli/src/main.rs

@@ -5,8 +5,12 @@ mod address;
 mod format;
 mod node;
 mod parse_node;
+mod parse_node_raw;
 mod psbt;
 
+#[cfg(test)]
+pub mod test_utils;
+
 #[derive(Parser)]
 #[command(name = "wasm-utxo-cli")]
 #[command(about = "CLI tool for Bitcoin UTXO operations", long_about = None)]

packages/wasm-utxo/cli/src/parse_node.rs

@@ -317,3 +317,26 @@ pub fn parse_tx_bytes_internal(bytes: &[u8]) -> Result<Node, String> {
         .map(|tx| tx_to_node(&tx, Network::Bitcoin))
         .map_err(|e| e.to_string())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_parse_psbt_bitcoin_fullsigned() -> Result<(), Box<dyn std::error::Error>> {
+        use crate::format::fixtures::assert_tree_matches_fixture;
+        use crate::test_utils::{load_psbt_bytes, SignatureState, TxFormat};
+        use wasm_utxo::Network as WasmNetwork;
+
+        let psbt_bytes = load_psbt_bytes(
+            WasmNetwork::Bitcoin,
+            SignatureState::Fullsigned,
+            TxFormat::Psbt,
+        )?;
+
+        let node = parse_psbt_bytes_internal(&psbt_bytes)?;
+
+        assert_tree_matches_fixture(&node, "psbt_bitcoin_fullsigned")?;
+        Ok(())
+    }
+}