cat(msg) appends a newline even if 'msg' doesn't have one

1 - The following works as expected in Positron, RStudio, and terminal R:

> cat("a\n")
a
> cat("\n")

> cat(character(0))
> 

2 - The following works as expected in RStudio and terminal R:

> cat("")
> 

but in Positron, there's a newline as well;

> cat("")

> 

3 - The following works as expected in terminal R:

> cat("a")
a> 

but in Positron and RStudio, there's a newline appended as well;

> cat("a")
a
> 

Session info

This is with R 4.5.1 running in:

Positron Version: 2025.09.0 build 139
Code - OSS Version: 1.103.0
Commit: 30e3d0a74e09a0f6640929822cb57a326671360e
Date: 2025-08-29T18:34:16.368Z
Electron: 37.2.3
Chromium: 138.0.7204.100
Node.js: 22.17.0
V8: 13.8.500258-electron.0
OS: Linux x64 6.14.0-29-generic

Reproduce the examples in Positron with R 4.5.1, comparing cat(""), cat("a"), cat("a\n"), and cat(character(0)) with terminal R and RStudio. Trace the Positron console output handling and identify where the extra newline is introduced; done means output matches the expected R behavior for all four cases.