When typing into contenteditable elements (e.g. LinkedIn post editor),
the synthetic event approach (Plan A) may fail silently — the events
fire but the editor's internal state doesn't update, leaving the
element empty.
This adds an automatic fallback: after Plan A, we verify the text was
actually inserted by checking element.innerText. If it wasn't, we
fall back to execCommand('insertText') which integrates natively with
most rich-text editors including LinkedIn, Quill, and Slate.js.
The fallback uses proper Selection/Range API to select-all before
replacing, and preserves the undo stack since execCommand is handled
by the browser natively.
Fixes#168
2f92a9cb32