Outside line-number border looks completely horrible

[GeronimoCastano]

Description

With Codly 1.3.1, a bordered code block with number-placement: "outside" has a square left border and rounded right corners, which looks asymmetrical and weird. The same block with number-placement: "inside" has a symmetric rounded border.

Reproduction

#import "@preview/codly:1.3.1": *

#show: codly-init
#codly(
  number-format: numbering.with("1"),
  number-placement: "outside",
  display-icon: false,
  display-name: false,
  radius: 20pt,
  inset: 10pt,
  fill: rgb("#b8f2e6"),
  zebra-fill: rgb("#ffd166"),
  stroke: 3pt + rgb("#0066ff"),
  lang-stroke: none,
)

```text
print("line 1")
print("line 2")
print("line 3")
print("line 4")
```

Changing number-placement to "inside" produces the symmetric result shown in the comparison below.

Expected

The outside-number border should follow the same rounded geometry as the code fill, with a consistent radius and stroke width on both sides.

Actual

The outside-number border looks completely wrong, asymmetrical and overall does not follow the block fill shape.

[GeronimoCastano]

For context, PR #138 addresses a separate fill-clipping issue: with outside line numbers, the code fill should be rounded as one whole block, including its left edge. This issue is specifically about the border rendering. Even on the right side, where the fill is already rounded, the border stroke is malformed and does not follow the shape correctly. These are separate problems.