Function validateSeedPhrase

validateSeedPhrase(words: string[]): SeedValidationResult
Validates a mnemonic seed phrase against the BIP39 standard with detailed feedback.

Checks (in order):
1. Word count must be 12 or 24.
2. Each word must exist in the BIP39 English wordlist.
3. Checksum must be valid.
Parameters
- words: string[]
  The mnemonic phrase to validate.
Returns SeedValidationResult
A result object with isValid, error, wordCount, and invalidWords.
Example
```
const result = validateSeedPhrase(['abandon', 'abandon', ..., 'art']);
if (!result.isValid) {
  console.error(result.error);
  console.log('Invalid words:', result.invalidWords);
}
```
- Defined in packages/core/src/seed.ts:100