walletError cause option appends the cause message to message #269

Expected Behavior

walletError({ code, message, cause }) in src/shared/errors.ts keeps message as given, so a site can attach the underlying error without changing the text that users, tests, and callers matching on error.message see.

Current Behavior

incur's BaseError sets message to ${shortMessage}\n\nDetails: ${cause.message} whenever cause is an Error, so passing cause changes the reported message. A spawn failure typed with cause: error reported Failed to run sqlite3 for the lock at <path>: spawn sqlite3 EACCES, then a blank line and Details: spawn sqlite3 EACCES, repeating the cause and breaking exact-message matches.

Possible Solution

Say on walletError that cause appends Details: <cause message> to message, with the given text kept on shortMessage, or let callers attach a cause without changing message.

Minimal Reproducible Example

walletError({ code: "E_RUNTIME", message: "failed", cause: new Error("boom") }).message is "failed\n\nDetails: boom".

Context

Hit while replacing bare Error rejections in src/payment/session-lock.ts with typed errors that keep their message text.

_{Logged by Brendan Ryan in tempoxyz/wallet-cli at 23c6345. Filed by Frog.}