feat(abstract-utxo): add supportedSdkBackends with validation

Introduce supportedSdkBackends property to gate backend availability
and validate SDK backend support before decoding PSBTs.

Co-authored-by: llm-git <llm-git@ttll.de>

Issue: BTC-2650

Author: OttoAllmendinger

modules/abstract-utxo/src/abstractUtxoCoin.ts

@@ -428,6 +428,11 @@ export abstract class AbstractUtxoCoin
     legacy: this.isMainnet(),
   };
 
+  protected supportedSdkBackends: { utxolib: boolean; 'wasm-utxo': boolean } = {
+    utxolib: this.isMainnet(),
+    'wasm-utxo': true,
+  };
+
   protected constructor(bitgo: BitGoBase, amountType: 'number' | 'bigint' = 'number') {
     super(bitgo);
     this.amountType = amountType;
@@ -615,6 +620,10 @@ export abstract class AbstractUtxoCoin
     }
 
     if (utxolib.bitgo.isPsbt(input)) {
+      if (this.supportedSdkBackends[decodeWith] !== true) {
+        throw new Error(`SDK support for decodeWith=${decodeWith} is not available on this environment.`);
+      }
+
       if (!this.supportedTxFormats.psbt) {
         throw new ErrorDeprecatedTxFormat('psbt');
       }