feat: add support for taproot descriptors

Add test fixtures and validation for taproot descriptor support. Handle Tr
type scriptpubkey length checks.

Issue: BTC-1829

Author: OttoAllmendinger

packages/wasm-miniscript/test/descriptorFixtures.ts

@@ -345,6 +345,12 @@ export const fixtures = {
       script: "a914767e9119ff3b3ac0cb6dcfe21de1842ccf85f1c487",
       checksumRequired: false,
     },
+    {
+      descriptor:
+        "tr(50929b74c1a04954b78b4b6035e97a5e078a5a0f28ec96d547bfee9ace803ac0,multi_a(2,xpub661MyMwAqRbcFXS2qwsTkaFc7PEpwDXWgY1Hx2MS7XywhW24sTjQzxiUgnGNW5v6DsW9Z8JcAqf8a22v21jDSA3DwLbbpt2ra3WbP83QNvP/0/0,xpub661MyMwAqRbcGfiaWcoeKLerFu3qRfy6zSYAwnmxSKW8JSauRajFsAsRHs2pV4q5rxkb4ynx4Bm8t54McTCp8V27s7XsdpD8T4s56etpjro/0/0,xpub661MyMwAqRbcH4HzWiCwmYajy1SXZngxHvpYDNEX4xjrDAneAm6rnpPuPPXcBRsSgxupDBmH2tzPHkikNrnLbsvTHemPFHSFbZxonZcCwFi/0/0))#82q34xv2",
+      script: "51207e8c409f0ab01197f9676efc3a9505f1f09ed0f21693e46a3aa3b6b54d437aa2",
+      checksumRequired: true,
+    },
   ],
   invalid: [
     {

packages/wasm-miniscript/test/test.ts

@@ -29,6 +29,7 @@ function getScriptPubKeyLength(descType: string): number {
     case "Pkh":
       return 25;
     case "Wsh":
+    case "Tr":
       return 34;
     case "Bare":
       throw new Error("cannot determine scriptPubKey length for Bare descriptor");
@@ -50,6 +51,7 @@ function assertKnownDescriptorType(descriptor: Descriptor) {
     case "Wsh":
     case "Wpkh":
     case "ShWpkh":
+    case "Tr":
       break;
     default:
       throw new Error("unexpected descriptor type " + descriptor.descType());
@@ -94,6 +96,7 @@ describe("Descriptor fixtures", function () {
           // FIXME(BTC-1337): xprvs with hardened derivations are not supported yet
           console.log("Skipping encoding test for fixture", fixture.descriptor, i);
         }
+
         assert.ok(Number.isInteger(descriptor.maxWeightToSatisfy()));
         assertKnownDescriptorType(descriptor);
         await assertEqualAst(__dirname + `/fixtures/${i}.json`, descriptor);