Book-side twin of the audio-survival test, closing H1's verification
list. Scenario: web push carries percentage + epubcfi + context_text;
a koreader-style percentage-only push from a second source within the
window detects a conflict; the user resolves with the CFI-carrying
side. The funneled resolution must land the winner's ENTIRE locator
pair — percentage 0.5, epubcfi, context_text together (the old direct
writer NULLed context_text and character_offset, breaking the coherent
pair the far-anchor work established) — and must not spawn a duplicate
pending conflict.