Lint/check for duplicate chunk titles before render

[jamespcollins]

Migrating posit-dev/positron#15461.

System details:

Positron and OS details:

Positron Version: 2026.08.0 build 331
Code - OSS Version: 1.124.0
Commit: a3a370d4187484ce962794408c76dab702978eaf
Date: 2026-08-05T17:02:37-07:00
Electron: 42.2.0
Chromium: 148.0.7778.97
Node.js: 24.15.0
V8: 14.8.178.14-electron.0
OS: Darwin arm64 25.5.0

Session details:

R 4.4.0
Quarto 1.7.32

Describe the issue:

When authoring qmd notebooks, especially for batch rendering/execution on an HPC cluster, a headache is having the job fail because quarto throws an error for a duplicate chunk title. This is hard to notice ahead of time in long qmds with many chunks.

Expected or desired behavior:

I would like a lint / problem check with underline + tooltip warning for duplicate chunk titles (e.g., "#| label: " value) in when editing qmd notebooks.

Thanks for considering!

[juliasilge]

Thanks for outlining what you're looking for, @jamespcollins!