Run Cell button not showing for code blocks with uppercase {R} in .qmd files

Bug description

I found a small but confusing inconsistency in the Quarto VS Code extension.
• When I write a code chunk in a .qmd file with lowercase {r}, VS Code shows the “Run Cell” button above the chunk.
• But if I use uppercase {R}, the Run Cell button does not appear.

Steps to reproduce

in qmd files:

x <- 1:5
mean(x)

(no Run Cell button shown)

Actual behavior

Expected behavior

x <- 1:5
mean(x)

(Run Cell button works as expected)

Your environment

VSCode
Version: 1.104.2 (Universal)
Commit: e3a5acfb517a443235981655413d566533107e92
Date: 2025-09-24T11:21:37.073Z
Electron: 37.3.1
ElectronBuildId: 12404162
Chromium: 138.0.7204.235
Node.js: 22.18.0
V8: 13.8.258.31-electron.0
OS: Darwin arm64 25.0.0

quarto extension
Identifier
quarto.quarto
Version
1.124.0
Last Updated
2025-09-30, 17:07:38

R extension
Identifier
reditorsupport.r
Version
2.8.6
Last Updated
2025-09-30, 17:30:31
Size
5.41MB

Reproduce the issue in a .qmd file using the shown uppercase {R} and compare it with lowercase {r}. Start by tracing the Quarto VS Code extension’s Run Cell handling for code-cell language labels; done means uppercase {R} shows the same Run Cell button as lowercase {r}.