Currently, rendering breaks when typing into a cursor at the end of a link:
- The DM extends the link until the first "word boundary"
- However, the browser CE continues the link either indefinitely (Firefox) or not at all (Chromium/Firefox)
- The inconsistency persists until the next re-render.
The DM behaviour cannot be replicated in current browser CEs (because IME stability constraints prevent re-rendering whilst typing text) and is not always desirable (because link text is often multi-word).
Instead, we should do the following:
# Show clearly in the UI whether the cursor is inside or outside the link.
# Spend a cursor press crossing into/out of a link (without changing the DM offset).
# Use unicorn-like image nodes to impose indefinite CE continuation inside links (and none outside).
# Calculate the DM insertion annotations from the observed CE ones.