feat: implement typed error taxonomy and custom error classes (#18)

[TheDEV111]

closes #18

📝 Overview & Summary

Currently, the SDK throws plain, generic Error instances throughout its modules. This forces consumers to use brittle string-matching patterns in try/catch blocks to programmatically distinguish between specific error conditions (e.g. invalid meta-addresses, RPC failures, or view-tag mismatches).

This PR resolves Issue #18 by implementing a granular, typed hierarchy of custom error classes under src/errors.ts (re-exported from the SDK root entry point). These custom classes extend the native JavaScript Error class (guaranteeing runtime backwards-compatibility) while carrying enumerable, structured metadata payloads, stable error codes, and dynamic documentation links.

---

🛠️ Detailed Scope of Changes

1. The Error Hierarchy (src/errors.ts)

We have established a robust abstract taxonomy dividing errors into five primary functional domains:

WraithError (Abstract Base)
├── WraithInputError
│   ├── InvalidMetaAddressError
│   ├── InvalidNameError
│   ├── InvalidSignatureError
│   └── InvalidScalarError
├── WraithCryptoError
│   ├── KeyDerivationFailedError
│   ├── ViewTagMismatchError
│   └── ECDHFailedError
├── WraithNetworkError
│   ├── RPCRequestError
│   ├── RPCRetryExhaustedError
│   └── RetentionExceededError
├── WraithContractError
│   ├── NameNotFoundError
│   ├── NameAlreadyRegisteredError
│   ├── InsufficientAuthError
│   └── ContractRevertError
└── WraithBuilderError
    ├── InsufficientBalanceError
    └── UnsupportedAssetError

2. Properties & Serialization Support

Every subclass instances includes:

• name: Automatically matches the class name.
• code: A stable serializable constant string (e.g. "WRAITH/INPUT/INVALID_SIGNATURE") to retain class identity across network boundaries.
• context: A structured object containing domain-specific parameters (e.g. statusCode, expectedLength, actualLength).
• docsLink: A direct link referencing the specific error details in the documentation guide.
• JSON Serialization: Native support via toJSON() on WraithError to ensure custom properties serialize cleanly with JSON.stringify(error).

3. Codebase-wide Refactoring

• Generic Throw Replacements: Swept all modules across all supported chains (CKB, EVM, Solana, and Stellar) and the core Wraith Agent Client to replace plain throw new Error(...) calls with their typed equivalents.
• JSDoc Enhancements: Updated @throws comments across public functions to document specific error behavior.

4. Testing & QA

• Unit Tests (test/errors.test.ts): Added 17 unit tests verifying instanceof correctness (including ancestor matching like WraithInputError), name/code/docsLink generation, property preservation, and serialization.
• Suite Adjustment: Updated existing signature-rejection test suites on all chains to expect the typed InvalidSignatureError exceptions.

5. Documentation

• User Guide (docs/errors.md): Wrote a complete, premium-quality developer guide containing the class tree, property mappings, stable codes reference table, and rich try/catch integration examples.
• Changelog (CHANGELOG.md): Noted the change in a new changelog file, warning developers about message string formatting adjustments.

---

⚠️ Impact & Migration Path

• Runtime Non-Breaking: Applications that catch exceptions as generic Error instances remain unaffected because all custom classes inherit from Error.
• Typing-Breaking for Brittle Matchers: Code relying on substring checks against error.message (e.g. .toThrow('Expected 65-byte signature')) will break. Integrators must update their catch statements to use modern instanceof checking:

import { InvalidSignatureError } from '@wraith-protocol/sdk';

try {
  const keys = deriveStealthKeys(badSig);
} catch (e) {
  if (e instanceof InvalidSignatureError) {
    console.error(`Expected signature length: ${e.context.expectedLength}`);
  }
}

---

✅ Verification & Testing Done

• Vitest Results: Ran pnpm test, verifying that all 151 unit and E2E tests successfully pass.
• Precommit Check: Format checking and TypeScript generation executed successfully under Husky hooks:

  ESM dist/index.js                 5.10 KB
  CJS dist/index.cjs                7.89 KB
  DTS dist/index.d.ts               8.62 KB
  ⚡️ Build success in 582ms

[drips-wave]

@TheDEV111 Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits

[truthixify]

The error hierarchy (src/errors.ts, 230 lines + 235 lines of tests) is the right shape. Same rebase situation.

git fetch origin
git rebase origin/develop
git push --force-with-lease

Keep src/errors.ts, test/errors.test.ts, the per-chain typed-throw migrations; resolve conflicts in files you didn't intend to rewrite by keeping develop's versions. Thanks @TheDEV111.