Support modifying output files names in post render script

Post render script is ran as part of renderProject
https://github.com/quarto-dev/quarto-cli/blob/7483c62fa9af0437f72b3341f9a1c53a22c58b66/src/command/render/project.ts#L857-L858

post render does allow access to output files
https://github.com/quarto-dev/quarto-cli/blob/7483c62fa9af0437f72b3341f9a1c53a22c58b66/src/command/render/project.ts#L876-L878

This post render step is done before other steps that use the output files
https://github.com/quarto-dev/quarto-cli/blob/7483c62fa9af0437f72b3341f9a1c53a22c58b66/src/command/preview/cmd.ts#L360-L371

This is specifically the compute of finalOutput that fails
https://github.com/quarto-dev/quarto-cli/blob/7483c62fa9af0437f72b3341f9a1c53a22c58b66/src/command/preview/preview.ts#L394-L398

It could happen that the output file's name is modified by the post render step. However, there is no mechanism to pass back this information for the rest of the process.

I see to choice here:

• Either supporting passing back information of modification

  • For example, QUARTO_PROJECT_OUTPUT_FILES or QUARTO_USE_FILE_FOR_PROJECT_OUTPUT_FILES with a modified by post render script, and read that for new output files

• Either document that this should not happen in post render script or quarto preview won't work.

For render, the final output is also computed, but if no found based on input name, it will just show nothing and not error like in preview
https://github.com/quarto-dev/quarto-cli/blob/7483c62fa9af0437f72b3341f9a1c53a22c58b66/src/command/render/cmd.ts#L269-L286

The real issue is the error at
https://github.com/quarto-dev/quarto-cli/blob/7483c62fa9af0437f72b3341f9a1c53a22c58b66/src/command/preview/preview.ts#L399-L401

leading to

ERROR: No output created by quarto render 02_filtering.qmd

Stack trace:
    at handleRenderResult (file:///Applications/RStudio.app/Contents/Resources/app/quarto/bin/quarto.js:91527:15)
    at renderForPreview (file:///Applications/RStudio.app/Contents/Resources/app/quarto/bin/quarto.js:91543:25)
    at eventLoopTick (ext:core/01_core.js:175:7)
    at async render (file:///Applications/RStudio.app/Contents/Resources/app/quarto/bin/quarto.js:91416:29)
GET: /Analysis/02_filtering.html (404: Not Found)

when post render modify the name of 02_filtering.html

Maybe not erroring and just previewing the base url (for index.html as a fallback) is better 🤷‍♂

Use case: Using post render script to rename output file was given as workaround to support adding date to output file name. See

• https://github.com/quarto-dev/quarto-cli/discussions/10732
• https://github.com/quarto-dev/quarto-cli/discussions/13052

Start with src/command/render/project.ts and trace how post-render output files flow into src/command/preview/cmd.ts and src/command/preview/preview.ts, especially finalOutput. Compare the related handling in src/command/render/cmd.ts and reproduce a post-render rename such as 02_filtering.html; done means preview can locate and serve the renamed output without the “No output created” error.