File Explorer: small cleanups

[ericpgreen2]

• Applies flex-none so carets and icons don't resize when the sidebar's width changes
• Uses <a> elements not <button> element for file navigation; moves the context menu <button> outside of the <a> tag
• Corrects the hover state for dotfiles
• Modifies e2e tests to identify files with full file path
• Adds a "No tables found" note for new projects without any tables
• Improves the default Model and Dashboard files
• Adds /.git as a protected directory

[briangregoryholmes]

Not sure if this PR was meant to address it, but the nav entries do still have nested interactive elements. The dropdown trigger is inside the <a> tag.

[ericpgreen2]

Not sure if this PR was meant to address it, but the nav entries do still have nested interactive elements. The dropdown trigger is inside the <a> tag.

Oh, missed that – fixed.