Fix API error fallback when structured payload is missing

[fhacloid]

Summary

• add a fallback in APIResponseError.Error() to show raw response body when models.ErrorPayload cannot be parsed
• include request Path in APIResponseError (captured from resp.Request.URL.RequestURI()) so fallback messages include the user request path
• add middleware tests covering fallback with and without path and request-path capture in newAPIResponseError
• document the updated APIResponseError fallback behavior in docs/architecture.md

Testing

• go test ./cmd/cycloid/middleware -run 'TestAPIResponseError|TestNewAPIResponseError_PathFallback' -count=1 ❌ (environment cannot download Go 1.25 toolchain)
• make format ❌ (missing Go 1.25 toolchain and gci in environment)
• make lint ❌ (missing Go 1.25 toolchain and golangci-lint in environment)

Linear Issue: CLI-109