core: one command for the seed, whichever way it arrives

create and import differed only in where the entropy came from and already
shared one store function, so they are one command with the source named:
/_wallet create new, or /_wallet create seed=<phrase>. Naming it means no
seed is generated by typing a prefix.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Rvc3HbiWBTqbAvRT45G5oX

bots/src/API/Docs/Commands.hs

@@ -455,7 +455,6 @@ undocumentedCommands =
     "APIWalletDelete",
     "APIWalletExportDerivedSecret",
     "APIWalletExportSeedMnemonic",
-    "APIWalletImport",
     "CheckChatRunning",
     "ConfirmRemoteCtrl",
     "ConnectRemoteCtrl",