core: export the secret of a single name key

/_wallet export gives the seed mnemonic, /_wallet export <account> <name>
gives the secret of one derived key, so a single name can be handed over
without the seed. Both are what a wallet takes on import: the mnemonic as a
recovery phrase, the secret as hex.

The commands are named for what they return, APIWalletExportSeedMnemonic
and APIWalletExportDerivedSecret, as the difference is which secret leaves
the device.

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

@@ -453,7 +453,8 @@ undocumentedCommands =
     "APIWallet",
     "APIWalletCreate",
     "APIWalletDelete",
-    "APIWalletExport",
+    "APIWalletExportDerivedSecret",
+    "APIWalletExportSeedMnemonic",
     "APIWalletImport",
     "CheckChatRunning",
     "ConfirmRemoteCtrl",

bots/src/API/Docs/Responses.hs

@@ -213,6 +213,7 @@ undocumentedResponses =
     "CRUserServersValidation",
     "CRVersionInfo",
     "CRWallet",
-    "CRWalletPhrase",
+    "CRWalletDerivedSecret",
+    "CRWalletSeedMnemonic",
     "CRWelcome"
   ]