Bibliography error for book when rendering to HTML while not specific in config

Let's set up project

> quarto create project book test-book
> cd test-book

Modify _quarto.yml to have only

format:
  docx: default

And then observe puzzling error here

❯ quarto render --to html
[1/4] index.qmd
[2/4] intro.qmd
[3/4] summary.qmd
[4/4] references.qmd

ERROR: Unable to determine proper path to use when computing bibliography path for index.html.

Stack trace:
    at bookBibliography (file:///C:/Users/chris/Documents/DEV_R/quarto-cli/src/project/types/book/book-bibliography.ts:105:11)
    at eventLoopTick (ext:core/01_core.js:153:7)
    at async bookBibliographyPostRender (file:///C:/Users/chris/Documents/DEV_R/quarto-cli/src/project/types/book/book-bibliography.ts:135:48)
    at async Object.bookPostRender [as postRender] (file:///C:/Users/chris/Documents/DEV_R/quarto-cli/src/project/types/book/book-render.ts:614:5)
    at async renderProject (file:///C:/Users/chris/Documents/DEV_R/quarto-cli/src/command/render/project.ts:808:7)
    at async Command.actionHandler (file:///C:/Users/chris/Documents/DEV_R/quarto-cli/src/command/render/cmd.ts:248:26)
    at async Command.execute (file:///C:/Users/chris/Documents/DEV_R/quarto-cli/src/vendor/deno.land/x/cliffy@v1.0.0-rc.3/command/command.ts:1948:7)
    at async Command.parseCommand (file:///C:/Users/chris/Documents/DEV_R/quarto-cli/src/vendor/deno.land/x/cliffy@v1.0.0-rc.3/command/command.ts:1780:14)
    at async quarto (file:///C:/Users/chris/Documents/DEV_R/quarto-cli/src/quarto.ts:163:5)
    at async file:///C:/Users/chris/Documents/DEV_R/quarto-cli/src/quarto.ts:185:5

and _quarto.yml does not have html specified in one of the format.

Originally posted by @cderv in https://github.com/quarto-dev/quarto-cli/issues/10427#issuecomment-2260098351

I believe

• Either this should work using html: default if we provide --to at CLI.
• Unless I missing something , and --to is supposed to be only on of the project format specified, and in that case we need to error ealier before any rendering probably.

Reproduce the project setup with quarto create project book test-book, the _quarto.yml containing only docx: default, and quarto render --to html. Start in src/project/types/book/book-bibliography.ts around bookBibliography, then follow book-bibliography.ts and book-render.ts post-render handling. Done means the CLI handles this configuration consistently, either rendering HTML successfully or reporting the format problem before rendering.