Code chunk decorations break after multiple/nested divs when using bracket colorization hack in Positron

Bug description

When using the bracket colorization hack from #670 to highlight fenced divs, code chunk decorations ("Run Cell | Run Next Cell | Run Above") disappear after a sequence of nested/multiple divs.

Steps to reproduce

In the following document, working-chunk-1 and working-chunk-2 show proper decorations, but the broken chunk loses all decorations:

---
title: "Test Code Decorations"
format: html
---

:::: {.callout-note}

```{r}
#| label: working-chunk-1

summary(mtcars)

```

:::

:::: {.callout-note}

```{r}
#| label: working-chunk-2

head(mtcars)

```

:::

:::: {.callout-note}

:::

:::: {.callout-note}

:::: {.callout-note}

:::

:::: {.callout-note}

:::

:::

:::: {.callout-note}

:::: {.callout-note}

:::

:::: {.callout-note}

:::

:::

:::: {.callout-note}

:::

:::: {.callout-note}

:::: {.callout-note}

:::

:::

:::: {.callout-note}

:::: {.callout-note}

:::

:::: {.callout-note}

:::

:::: {.callout-note}

:::

:::: {.callout-note}

:::

:::: {.callout-note}

:::

:::

:::: {.callout-note}

:::


```{r}
#| label: broken

nrow(mtcars)

```

```{r}
#| label: also-broken

nrow(mtcars)

```

Actual behavior

After the sequence of nested/empty divs, the broken chunk shows no decorations. In real documents with many nested callout blocks, this progressively affects all subsequent chunks.

Expected behavior

All R chunks should display "Run Cell | Run Next Cell | Run Above" decorations regardless of preceding div structure.

Your environment

Positron Version: 2025.12.0 (user setup) build 105
Code - OSS Version: 1.105.0
Commit: 98537e9935afc48311e32033c6518a3c89829789
Date: 2025-11-20T07:45:30.453Z
Electron: 37.6.0
Chromium: 138.0.7204.251
Node.js: 22.19.0
V8: 13.8.258.32-electron.0
OS: Windows_NT x64 10.0.26100

Reproduce the supplied Quarto document in Positron and compare R chunk decorations before and after the nested and empty fenced divs. Trace the code-chunk decoration handling; done means all subsequent chunks retain the "Run Cell | Run Next Cell | Run Above" decorations. The issue names no source file or test path, so those must be located first.