## Summary
Fixes the information-disclosure regression introduced by #1335 (item 1
of #1337).
`ListServersError` passed the raw `err` into
`huma.Error500InternalServerError(...)`. huma serializes extra error
args into the response body's `errors` array (`ErrorModel.Errors`,
`json:"errors,omitempty"`), so on the **public, unauthenticated** `GET
/v0/servers` endpoint a genuine DB failure echoed the internal wrapped
error from `internal/database/postgres.go` (`error iterating rows: <pgx
error>`) back to the client. pgx/pgconn errors can carry SQLSTATE codes,
constraint/table/column names, and internal messages (CWE-209).
## Change
- Drop `err` from the 500 call so only the generic message is returned;
keep `log.Printf` for the server-side detail — matching the sibling
handlers (`servers.go:190/220`, `edit.go`, `status.go`).
- Add a regression test
(`TestListServersError_realFailureDoesNotLeakDetail`) that marshals the
500 error and asserts the internal detail is absent from the
client-visible body. Existing tests only asserted status codes, which is
why the leak slipped through.
The 499 client-cancelled path is unchanged (the client has already
disconnected, so nothing is leaked there).
## Test plan
- [x] `go test ./internal/api/handlers/v0/... -run ListServersError`
(3/3 pass)
- [x] `go build ./...`, `go vet`, `golangci-lint` (no new findings in
changed files)
## Note
This leaves the non-security items in #1337 (correcting the `superfluous
WriteHeader` claim, `statusClientClosed` const reuse, broader
cancellation-guard scope) for separate follow-up. Closing #1337 here
since the only security-impacting item is addressed; reopen/split if
you'd prefer to track the nits independently.
Closes#1337🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Maps context.Canceled from ListServers to 499 and skips the error-level log on client disconnect.
Merged as-is per maintainer decision; known follow-up tracked in #1337 (500-path error-detail leak + WriteHeader claim correction + nits).
