[Gain peace of mind with seed phrase] 13th word/password support

I would love to be able to store my seed phrase in a paper with the peace of mind that if someone discovers it, I'm safe because they don't have my 13th word.

I think it's crucial. Because it lets you protect all your seed phrases in paper with an extra word that can be stored separately or that can exist only in your brain. So you eliminate the fear of someone seeing your seed phrases.

With this feature, you can sleep like a baby at night knowing that if someone finds your seed phrase, they can't access the funds because they don't have the extra word.

No file, package, entry point, or test is named. Start by locating the seed phrase generation, import, and wallet derivation code in the TypeScript packages, then determine the required passphrase standard and compatibility behavior. Done should include an agreed design, implementation, and tests covering creation and recovery with the additional word.

Written by the indexing model from the issue text.