Warn when Quarto project uses non-web-servable output formats (pdf, docx, etc.)

[zackverham]

Context

In #4021 we removed the --to html flag from the "Render Your Project" command, which was silently overriding per-file format declarations (breaking format: revealjs, etc.). This was fixed in #4048.

With that fix, quarto render now respects all declared formats — including non-web-servable ones like format: pdf or format: docx. These formats aren't valid for Posit Connect deployment, and the current pipeline will fail or produce broken content downstream when it can't find the expected .html output.

Proposal

Add a warning in the inspection layer (QuartoDetector / QuartoInspectOutput) when unsupported output formats are detected. The formats field from quarto inspect output already surfaces this information.

Possible approaches:

• Warn at inspection time if the only declared format is non-HTML (pdf, docx, etc.)
• Warn at render time if quarto inspect reveals formats that won't produce web-deployable output
• Surface the warning in the UI so the user understands why their content may not deploy correctly

Current state

• QuartoInspectOutput.formats only types html and revealjs — other format keys are silently ignored
• The static alternative builder (buildStaticAlternative) assumes HTML output throughout
• There is no validation or user-facing warning for unsupported formats

Related

• Rendering a Quarto website from the Publisher panel produces different output from quarto render when a page uses revealjs #4021 — original bug report (revealjs rendered as HTML)
• Fix Quarto website rendering and deployment for mixed-format projects #4048 — fix removing --to html

[dotNomad]

Warn at inspection time if the only declared format is non-HTML (pdf, docx, etc.)

I'm not sure if we have any inspection time warnings right now

Warn at render time if quarto inspect reveals formats that won't produce web-deployable output

This and at publish time feel right to me. We could also put something in the home view sidebar if we can detect a invalid format