Adjacent-link separator dropped when the second link is wrapped in formatting #96

Follow-up from the second review of #92.

SeparateUnwrappedBlocks.kt emits the separator between adjacent links right before the <a> mark. If an inline wrapper is already open, that puts the separator inside it. dropHtmlStructuralWhitespace then drops it, because leftQualifies is false after an opening tag. So links wrapped in formatting still merge into one word.

Repro

<p><a href=u>x</a><b><a href=v>y</a></b></p> (the Hacker News masthead shape, reversed) still renders [x](u)**[y](v)**.

Fix

Emit the separator before the first inline mark opened since the previous token.