Expand description
The one error type every call returns.
The failures a caller actually branches on are separate variants — bad
credentials, a body the server refused as too large, a 409 that survived
the retry, a bundle that cannot satisfy its own manifest. Everything else
the server classified itself arrives as Error::Server, carrying the
wire ErrorCode rather than a flattened string, so a caller can match on
RenderFailed versus Internal without parsing prose.