Document every error this can return

Users hit an error code and find nothing when they search it.

Produce documentation for the errors in the code below.

Give a table, one row per error, with: code or identifier, the exact message text a user sees, what actually causes it, whether it is the caller's fault or ours, whether retrying helps, and the fix.

Then, for the errors users will meet most often, write a short section each: what happened, the most likely cause, the check that confirms it, and the resolution. Use the exact message as the heading so a search engine finds it.

Also report:
- Errors with identical or near-identical messages that a user could not tell apart
- Errors whose message does not say what to do next
- Failure paths that produce no error at all and fail silently

Do not invent error conditions that are not in the code.

Code:

Reference and API docs. The lookup layer: function docs, config options, error codes and examples worth copying.