quarto create-project must preserve case of the created file

[cscheid]

In 1.4,

• quarto create-project ~/somePath would create somePath.qmd
• quarto create, then selecting name somePath, would create SomePath.qmd. This is bad. That was quarto create capitalizes the qmd file name #8401.

The fix for #8401 causes quarto create-project ~/somePath to create somepath.qmd. This is also bad and breaks RStudio.