refactor(abstract-substrate): replace any cast with typed intersection for coinSpecific.material

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: nvrakesh06

modules/abstract-substrate/src/abstractSubstrateCoin.ts

@@ -20,6 +20,7 @@ import {
   RecoveryTxRequest,
   SignedTransaction,
   TssVerifyAddressOptions,
+  TransactionPrebuild,
   TxIntentMismatchRecipientError,
   UnexpectedAddressError,
   verifyEddsaTssWalletAddress,
@@ -151,7 +152,8 @@ export class SubstrateCoin extends BaseCoin {
     // transactions built against a chain spec version newer than the SDK's hardcoded metadata.
     // Without this, the factory falls back to its hardcoded material and misidentifies the call
     // pallet (e.g. reads a Balances transfer as treasury.disbursement after a chain upgrade).
-    const prebuildMaterial = (txPrebuild as any).coinSpecific?.material as Material | undefined;
+    const prebuildMaterial = (txPrebuild as TransactionPrebuild & { coinSpecific?: { material?: Material } })
+      .coinSpecific?.material;
     if (prebuildMaterial && typeof factory.material === 'function') {
       factory.material(prebuildMaterial);
     }