feat(sdk-coin-kaspa): implement Kaspa SDK module

modules/sdk-coin-kaspa/.eslintignore

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+node_modules
+.idea
+public
+dist
+

modules/sdk-coin-kaspa/.eslintrc.json

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+{
+  "extends": "../../.eslintrc.json",
+  "rules": {
+    "@typescript-eslint/explicit-module-boundary-types": "error",
+    "indent": "off"
+  }
+}

modules/sdk-coin-kaspa/.mocharc.yml

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+require: 'tsx'
+timeout: '60000'
+reporter: 'min'
+reporter-option:
+  - 'cdn=true'
+  - 'json=false'
+exit: true
+spec: ['test/unit/**/*.ts']

modules/sdk-coin-kaspa/README.md

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+# @bitgo/sdk-coin-kaspa
+
+BitGo's SDK module for the **Kaspa (KASPA)** blockchain.
+
+## Overview
+
+Kaspa is a proof-of-work blockchain based on the GHOSTDAG protocol (a generalization of Nakamoto consensus), enabling high block rates. This module implements Kaspa's UTXO model with **secp256k1 Schnorr signatures** (BIP-143-like sighash) and the custom **kaspa/kaspatest** bech32 address format.
+
+Supported coin identifiers:
+
+- `kaspa` — Kaspa mainnet
+- `tkaspa` — Kaspa testnet
+
+## Features
+
+- Key pair generation (secp256k1)
+- Address derivation (kaspa bech32 P2PK Schnorr)
+- UTXO transaction building
+- Schnorr signing and verification (Blake2b-256 sighash)
+- TSS/MPC support (ECDSA algorithm)
+- Full serialization round-trip (hex/JSON)
+
+## Installation
+
+```bash
+yarn add @bitgo/sdk-coin-kaspa
+```
+
+## Usage
+
+### Register with BitGo SDK
+
+```typescript
+import { register } from '@bitgo/sdk-coin-kaspa';
+register(bitgo);
+```
+
+### Key Pair
+
+```typescript
+import { KeyPair } from '@bitgo/sdk-coin-kaspa';
+
+// Generate a random key pair
+const kp = new KeyPair();
+const { pub, prv } = kp.getKeys();
+
+// Derive address
+const mainnetAddress = kp.getAddress('mainnet');
+const testnetAddress = kp.getAddress('testnet');
+```
+
+### Build and Sign a Transaction
+
+```typescript
+import { TransactionBuilderFactory } from '@bitgo/sdk-coin-kaspa';
+import { coins } from '@bitgo/statics';
+
+const factory = new TransactionBuilderFactory(coins.get('kaspa'));
+const builder = factory.getBuilder();
+
+builder
+  .addInput({
+    transactionId: '<prev-tx-id>',
+    transactionIndex: 0,
+    amount: '100000000', // 1 KASPA in sompi
+    scriptPublicKey: '<spk>',
+    sequence: '0',
+    sigOpCount: 1,
+  })
+  .to('<recipient-kaspa-address>', '99998000')
+  .fee('2000');
+
+const tx = await builder.build();
+tx.sign(Buffer.from(privateKeyHex, 'hex'));
+
+const broadcastPayload = tx.toBroadcastFormat(); // JSON string for RPC
+```
+
+## Module Structure
+
+```
+src/
+├── kaspa.ts                    # Kaspa mainnet coin class
+├── tkaspa.ts                   # Kaspa testnet coin class
+├── register.ts                 # SDK registration
+├── index.ts
+└── lib/
+    ├── constants.ts            # Chain constants (prefixes, decimals, fees)
+    ├── iface.ts                # TypeScript interfaces
+    ├── keyPair.ts              # secp256k1 key pair
+    ├── sighash.ts              # Blake2b-256 Schnorr sighash
+    ├── transaction.ts          # Transaction class (sign/verify/explain)
+    ├── transactionBuilder.ts   # UTXO transaction builder
+    ├── transactionBuilderFactory.ts
+    ├── utils.ts                # Address validation and encoding
+    └── index.ts
+test/
+├── fixtures/
+│   ├── kaspa.fixtures.ts       # Deterministic test vectors
+│   └── kaspaFixtures.ts        # Synthetic test fixtures
+└── unit/
+    ├── coin.test.ts
+    ├── keyPair.test.ts
+    ├── transaction.test.ts
+    ├── transactionBuilder.test.ts
+    ├── transactionFlow.test.ts
+    └── utils.test.ts
+```
+
+## Address Format
+
+Kaspa uses a custom cashaddr-like bech32 encoding:
+
+- Mainnet: `kaspa:<bech32-encoded-data>`
+- Testnet: `kaspatest:<bech32-encoded-data>`
+- Version byte `0` = Schnorr P2PK (x-only secp256k1 pubkey)
+
+## Signing
+
+Kaspa uses **Schnorr signatures over secp256k1** with a **Blake2b-256** sighash. The sighash preimage follows the Kaspa BIP-143-like specification. Each input is signed independently, producing a 65-byte signature: 64 bytes Schnorr + 1 byte sighash type.
+
+## References
+
+- [Kaspa Website](https://kaspa.org/)
+- [Kaspa BIP-143-like SigHashes](https://github.com/kaspanet/docs/blob/main/Specs/BIP143-like%20SigHashes.md)
+- [Kaspa RPC API](https://kaspa.aspectron.org/docs/)

modules/sdk-coin-kaspa/package.json

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+{
+  "name": "@bitgo/sdk-coin-kaspa",
+  "version": "1.0.0",
+  "description": "BitGo's SDK coin library for Kaspa (KASPA)",
+  "main": "./dist/src/index.js",
+  "types": "./dist/src/index.d.ts",
+  "scripts": {
+    "build": "yarn tsc --build --incremental --verbose .",
+    "fmt": "prettier --write .",
+    "check-fmt": "prettier --check '**/*.{ts,js,json}'",
+    "clean": "rm -r ./dist",
+    "lint": "eslint --quiet .",
+    "prepare": "npm run build",
+    "test": "npm run coverage",
+    "coverage": "nyc -- npm run unit-test",
+    "unit-test": "mocha"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/BitGo/BitGoJS.git",
+    "directory": "modules/sdk-coin-kaspa"
+  },
+  "author": "BitGo SDK Team <[email protected]>",
+  "license": "MIT",
+  "engines": {
+    "node": ">=20"
+  },
+  "lint-staged": {
+    "*.{js,ts}": [
+      "yarn prettier --write",
+      "yarn eslint --fix"
+    ]
+  },
+  "publishConfig": {
+    "access": "public"
+  },
+  "nyc": {
+    "extension": [
+      ".ts"
+    ]
+  },
+  "dependencies": {
+    "@bitgo/sdk-core": "^36.40.0",
+    "@bitgo/secp256k1": "^1.11.0",
+    "@bitgo/statics": "^58.35.0",
+    "bignumber.js": "9.0.0",
+    "blakejs": "^1.2.1"
+  },
+  "files": [
+    "dist"
+  ]
+}

modules/sdk-coin-kaspa/src/index.ts

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+export * from './kaspa';
+export * from './tkaspa';
+export * from './lib';
+export * as KaspaLib from './lib';
+export * from './register';